While I agree that this question is relatively straight-forward, whenever Test Takers see a drop in scores on Test Day, the reason is almost always SILLY/LITTLE MISTAKES. As such, it's important to be sure that you have the correct answer to a question that you "think" is easy/straight-forward/gettable. This question can be solved by TESTing VALUES.
We're told to calculate the cost of 7 days of deliveries.
On each day, there's a cost for the delivery itself (D DOLLARS) and a cost per item delivered (C CENTS/item). Note the difference in UNITS. During the week, we're told that an average of X items are delivered each DAY.
Let's TEST VALUES:
D = 2
C = 3
X = 10
So, per day, the Total Cost = 2 dollars + 3 cents(10 items) = $2.30 per day
For 7 days, that's 7($2.30) = $16.10
Now, we just have to check the answers and find the match IN DOLLARS...
Answer A = 7(3)(2)(10)/100 = 420/100 = 4.2 dollars. NOT a match
Answer B = 2 + 7(10(3)/100 = 2 + 210/100 = 4.1 dollars. NOT a match
Answer C = 7(2) + 10(3)/100 = 14.3 dollars. NOT a match
Answer D = 7(2) + 7(10)(3)/100 = 16.1 dollars. This IS a MATCH
Asnwer E = 7(3)(2)(10) = 420 dollars. NOT a match
GMAT assassins aren't born, they're made,