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: One property of liquids is that they have a definite  
 (A) flexibility (B) temperature (C) volume (D) shape

SOLUTION: C

PROBLEM: Two forms of boron are naturally occurring, boron-10 and boron-11. What difference exists between a boron atom with a 10 atomic mass units (amu) and a boron atom with 11 atomic mass units (amu)?  
 (A) amount of neutrons (B) number of electrons (C) size of protons and neutrons (D) size of electrons and electron cloud

SOLUTION: A

PROBLEM: A student is measuring the boiling point of a salt and water mixture. He takes one temperature measurement of 105°C. Which is the best way to ensure the results are valid?  
 (A) repeat the investigation (B) change the volume of water (C) add more salt to the mixture (D) do the investigation without salt

SOLUTION:
A