#### Answer

C

#### Work Step by Step

Option A is incorrect. During month 3, the puppy gained 3 kg, but in month 4, the puppy gained 5 kg.
Option B is incorrect. The puppy's mass was exactly 5 kg at the start of the diet.
Option D is incorrect. The puppy actually gained 8 kg from the new diet.
Option C is correct. The puppy did gain 5 kg from month 3 and month 4.