Please help me im very behind

I think its d. a13=23

Plz correct me If I am wrong  

Step-by-step explanation:

in simplified version   it would be x ≤-4

step-by-step explanation:

multiply each term in x ≤-4 by -1

answer: the sun

explanation:

water cycle describes the evaporation of water from earth's surface, formation of clouds and precipitation water back onto the surface of earth. seventy percent of the earth is covered with water in the form of seas and oceans. the heat of the sun causes the evaporation of water from the surface of the ocean. the water vapors rise and condense to form water droplets. the collection of these water droplets form clouds which rain down again.

the evaporation of the oceans surface water as part of the water cycle is caused by the sun