Wound it be one that dissolves ?
The answer is A, because it’s the first one
Answer:
B
Explanation:
Spectroscopy measures electromagnetic radiation.
Answer:
The first answer is W and Z, since they appear to be a period apart. Dont know the second question. I did what I could, hope someone can answer the second.
Answer:

Explanation:
The attached figure shows the whole description. Considering the applied force is 100 N.
The acceleration of both blocks A and B, 
Firstly calculating the mass m using the second law of motion as :
F = ma
m is the mass


m = 125 kg
It suddenly encounters a surface that supplies 25.0 N a friction, F' = 25 N



So, the new acceleration of the block is
. Hence, this is the required solution.