Aclass wants to find the ideal temperature for plants to grow in a terrarium. if the students set up several terrariums, what should they do to get the best results? a. plant different kinds of plants in each terrarium. b. use a light bulb with different brightness in each terrarium. c. add different amounts of water to each terrarium d. use different fertilizers in each terrarium

It would be B because you want to know which TEMPERATURE is the best for the plant. Different brightness for a bulb will give different amounts of heat. Since the amount of heat is your INDEPENDENT VARIABLE, you have to change the amount of heat for each plant, so the brightness of bulbs. Therefore, B is your answer!

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.