Length of Day (how does it affect plants)

Day length helps plants to regulate their internal clock

source: g00gle

When the day length is fewer than 10 hours, most plants do not grow. Even if the temperature is kept within the ideal range — say, in a climate-controlled greenhouse — most plants will go dormant until the magical 10 hours of sunshine per day arrives.

Explanation:

the answer would be knowledge about cars!

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds