TASK DEFINITION: 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.
PROBLEM: A student plans to design a new toothpaste tube that will give the same amount of toothpaste every time it is squeezed. Which should the student do first when designing the new tube?  
 (A) make a data table of amounts of toothpaste (B) gather building materials (C) create models of old toothpaste tubes (D) draw a few possible solutions

SOLUTION: D

PROBLEM: Robert is a fisherman who wants to find a way to catch more fish. He decided to try different sizes of hooks. Robert caught 4 catfish, 3 trout, and 7 perch while using worms for bait. Which is the independent (manipulated) variable in Robert's investigation?  
 (A) type of bait (B) size of hook (C) type of fish caught (D) number of fish caught

SOLUTION: B

PROBLEM: 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

SOLUTION:
C