A sample of ammonium chloride decomposes on heating. Solid ammonium chloride -> ammonia gas + hydrogen chloride gas
A total of 2.4 x 1021 molecules of gas is formed.
How many hydrogen atoms are present in the gaseous products?
A 1.2 x 1021
B 2.4 x 1021
C 4.8 x 1021
D 9.6 x 1021

the answer is barium and copper bromide

the answer is b because, investigating whether another species of moth also drinks tears might be interesting, but it would not directly explain why this species of moth does.

to explain why this species of moth drinks tears, the scientist could ask: "what nutrients that moths need are in elephant tears? "

the scientist could experiment with moth repellent or oter ways to keep the moths away, but that would not answer his original question.