Although amyotrophic lateral sclerosis, or ALS, typically causes death

OA should be C.

A. typically causes death within 3 to 5 years of the onset of symptoms, on average, the famous physicist Stephen Hawking has defied the odds, in contrast,

"in contrast" is not required with Although. Also, typically and average cause redundancy when used together.

B. causes death within 3 to 5 years of the onset of symptoms, on average, the famous physicist Stephen Hawking has defied the odds, in contrast,

Same as A.

C. typically causes death within 3 to 5 years of the onset of symptoms, the famous physicist Stephen Hawking has defied the odds. CORRECT
"in contrast" is omitted and "average" is also not used.

D. causes death within 3 to 5 years of the average onset of symptoms, the famous physicist Stephen Hawking has defied the odds, by contrast,

Same as A.

E. typically causes death within 3 to 5 years of the average onset of symptoms, the famous physicist Stephen Hawking has defied the odds

Same as A. Also the sentence makes no sense.

Hence option C

+1 for C !!
Use of "in contrast" in A and B and "by contrast" in D is wrong.
Also E uses average in the wrong place.

defied the odds + in/by contrast - redundant - Eliminate A, B & D

E - of the average onset of symptoms - illogical - OUT

C is the answer

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.