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:
A research study concluded that people who work longer hours increase their chances of having higher blood pressure. This conclusion was developed from a study of 200 men of different ages. How is this investigation biased?  
 (A) The sample size was too large. (B) Scientists did not run the study. (C) Women were excluded from the study. (D) No medication was given to the men.
answer:
C


question:
The fur of some animals becomes thicker in the winter and is shed in the spring. These observations show how animals  
 (A) respond to changes in the environment (B) move from place to place to survive (C) store fat for the winter (D) compete with other animals for food
answer:
A


question:
A student filled three beakers, each with 50 milliliters of liquid water. The student cooled Beaker 1 to form ice. The student heated Beaker 2 to form water vapor (gas). Beaker 3 remained at room temperature. What process takes place when liquid water changes to a vapor (gas)?  
 (A) condensation (B) evaporation (C) freezing (D) melting
answer:

B