Answer:
Option D. -3.9 will be the answer.
Step-by-step explanation:
Change in weight of the whale in first week = (-2.1) pounds
Change in weight of the whale in second week = (+0.3) pounds
Change in weight of the whale in 3rd week = (-1.7) pounds
Change in weight of the whale in 4th week = -0.4 pounds
Total change in weight over the period of 4 weeks = - 2.1 + 0.3 - 1.7 - 0.4
= -3.9 pounds
Therefore, Option D. -3.9 will be the answer.