Because glucerin is hotter so it decreases faster
Answer: I looked it up and it says something about the waves traveling in a solid but I don’t know if that’s correct.
Answer:
The coupled velocity of both the blocks is 1.92 m/s.
Explanation:
Given that,
Mass of block A, 
Initial speed of block A, 
Mass of block B, 
Initial speed of block B, 
It is mentioned that if the two blocks couple together after collision. We need to find the common velocity immediately after collision. We know that due to coupling, it becomes the case of inelastic collision. Using the conservation of linear momentum. Let V is the coupled velocity of both the blocks. So,

So, the coupled velocity of both the blocks is 1.92 m/s. Hence, this is the required solution.
It is B since they are traveling at the same speed one is positive so the other had to be negative hope this helps;)))))