John is conducting an experiment that involves melting ice cubes. Which of the following is most important for John to collect reliable data? A. The outcome needs to be controlled.

B. An unbiased observer must witness the experiment.

C. Technology needs to be used to determine the results.

D. Only one variable should be tested during the experiment.

Why is rain likely when warm, moisture-laden air meets cold air? a) the lighter warm air will rise and cool down, causing condensation and rain. b) the cold air moves faster and pushes the warm air away, causing condensation and rain. c) the moisture in the warm air condenses on contact with the cold air, causing rain to fall. d) the cold air mixes with the warm air, reducing its temperature causing moisture to condense.