Studies on thoroughbred racing displayed that if show-horses rest adeq

A simple thumb rule is that in cases of conditional sentences involving universal or factual happenings, the conditional sub clause will be represented by the simple present tense of the verb, while the main clause will be fixed with either a simple present or the simple future.

As per this copy- book style, E is the only fitting answer

Look at this link with a similar format of which I think this is a simulation a-study-commissioned-by-the-department-of-agriculture-showed-91173.html

A good concept to remember

My doubt for this question is how to know whether use a verb after "than" such as are ,will ,do etc. Explanation with examples is highly appreciated and kudos as well.

Specific to this question, I could eliminate A,B & C based on 'rest-race' parallelism, and eliminate D on the basis of present perfect tense; even without reaching till any of the action verbs.

Coming to your question, consider the following sentences

1. As a teacher, John takes less salary than a driver.
The comparison is between John and the driver. This is correct.

2. John's salary is less than a driver.
John's salary is being compared to driver. This is wrong.

3. John's salary is less than that of a driver.
'John's salary is less than the salary of a driver'. This sentence is also fine.

4. As a teacher, John takes less salary than a driver does.
The comparison is between John's action (taking) and a driver's action. This is also fine.

More ex. on 1 & 4
a. Cheetah runs faster than tiger.
I am comparing the cheetah with the tiger.

b. Cheetah runs faster than tiger does.
I am comparing the cheetah's action (running) with that of the tiger.

5. John's salary is less than a driver's.
A driver's is concision of driver's salary. Here, I am comparing John's salary and the driver's salary. This sentence is also perfectly fine.

Coming back to your sentence now and rephrasing the present perfect to simple present in D
D. race on synthetic surfaces, they are less likely to sustain an injury or illness than do those exhausted
we are comparing actions - sustain is the action word
E. race on synthetic surfaces, they are less likely to sustain an injury or illness than those exhausted
we are comparing the horses

I would say both are good (meaning-wise and grammar-wise)

Studies on thoroughbred racing displayed that if show-horses rest adequately between competitions and raced on synthetic surfaces, they will be less likely to sustain an injury or illness than do those exhausted from rigorous training schedules.

If (simple present tense),then (simple present/future)

A. raced on synthetic surfaces, they will be less likely to sustain an injury or illness than do
rest and raced ; not parallel ; Incorrect

B. raced on synthetic surfaces, they are less likely to sustain an injury or illness than
rest and raced ; not parallel ; Incorrect

C. race on synthetic surfaces, they sustained fewer injuries or illnesses than do
do not follow if,then structure ; Incorrect

D. race on synthetic surfaces, they have been less likely to sustain an injury or illness than do
do not follow if,then structure ; Incorrect

E. race on synthetic surfaces, they are less likely to sustain an injury or illness than
Correct


I am confused b/w 'than' and 'than do'

They..... than those exhausted from rigorous training schedules.
They ...(sustain) than do(sustain) those

How do we make comparision ?

Experts pls help

Studies on thoroughbred racing displayed that if show-horses rest adequately between competitions and raced on synthetic surfaces, they will be less likely to sustain an injury or illness than do those exhausted from rigorous training schedules.

If (simple present tense),then (simple present/future)

A. raced on synthetic surfaces, they will be less likely to sustain an injury or illness than do
rest and raced ; not parallel ; Incorrect

B. raced on synthetic surfaces, they are less likely to sustain an injury or illness than
rest and raced ; not parallel ; Incorrect

C. race on synthetic surfaces, they sustained fewer injuries or illnesses than do
do not follow if,then structure ; Incorrect

D. race on synthetic surfaces, they have been less likely to sustain an injury or illness than do
do not follow if,then structure ; Incorrect

E. race on synthetic surfaces, they are less likely to sustain an injury or illness than
Correct


I am confused b/w 'than' and 'than do'

They..... than those exhausted from rigorous training schedules.
They ...(sustain) than do(sustain) those

How do we make comparison ?

Experts pls help

parallelism is the main issue here.
between X and Y
X than Y

Studies on thoroughbred racing displayed that if show-horses rest adequately between competitions and race on synthetic surfaces, they are less likely to sustain an injury or illness than those exhausted from rigorous training schedules.

Rule:
If ... (simple present condition)... , then ..( simple present or simple future result)...