How can erosion be both constructive and destructive?

Well, erosion can be destructive because it could carry soil, or sand, or rock, or whatever away from a place and destruct landforms... but it is constructive because when it moves that stuff, it puts it in a new place, slowly making new landforms.

Erosion can destroy things that were already there and burn them.
But the lava that cools down can form new things. It can help plants grow from the cracks.

(HOPE THIS WAS HELPFUL)

The sun's parallax would be 180 degrees, greater than which you can't get.  so a. would be your anwser 

2cool and cold temperature unless its an ever green tree