instruction:
You are given a science question (hard-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.
question:
If 100 grams of vinegar and 5 grams of baking soda are poured in a container, a small amount of gas will be produced. What will the final mass of the products be if the gas is trapped in the container?  
 (A) 100 grams (B) 104 grams (C) 105 grams (D) 110 grams
answer:
C


question:
Farmers plant fruit trees in an area that was once a grassy meadow. Which will most likely happen to the rabbits living in the meadow?  
 (A) They will learn to eat fruit. (B) They will learn to climb trees. (C) The number of their young will increase. (D) The size of their population will decrease.
answer:
D


question:
A medical research team is trying to determine whether a cream that is rubbed on the chest will help reduce the coughing associated with a particular illness. The team conducts the research using several groups of people. Which step will most likely result in producing a dependent (responding) variable that will help validate their research?  
 (A) using a different amount of people in each trial (B) writing down the names of the people in the study (C) monitoring the reaction of each person in the study (D) applying the same amount of cream to each person
answer:

D