TASK DEFINITION: You are given a question or fill-in-the-blank question, two answer options (Option1 and Option2) and an Explanation. Your task is to find the correct answer (return the string of the correct option, not option1/2) for the given question from the given options and using explanation.
PROBLEM: Question: Clare stopped rubbing two sticks together. The sticks became 
 Option1: hot 
 Option2: cold 
 Explanation: Friction causes the molecules on rubbing surfaces to move faster, so they have more heat energy.

SOLUTION: cold

PROBLEM: Question: Katie is rubbing her hands on her leg. One hand rubs fast, the other hand rubs slow. The hand that will be cooler in the end is the one that moves 
 Option1: faster 
 Option2: slower 
 Explanation: Friction causes the molecules on rubbing surfaces to move faster, so they have more energy. This gives them a higher temperature, and they feel warmer.

SOLUTION: slower

PROBLEM: Question: An _____ pulse rate is a sign of more oxygen to cells. 
 Option1: increased 
 Option2: decreased 
 Explanation: This causes the delivery of less oxygen to the cells, and this stimulates the heart rate via adrenalin, so that pulse rate increases in an effort to deliver enough oxygen to cells.

SOLUTION:
decreased