How is a wavelength measured? a. from crest to crest b. from trough to crest c. from sea level to trough d. from sea level to crest

Can someone me with this plz? ! i'm putting 20 points on it!

Based on what you know about the location of the earth in relation to the sun, why is this called the goldilocks zone in other galaxies? a. it's a region that exhibits a weak gravitational pull, thus maintaining a safe distance from the sun. b. it's an area that doesn't experience any major weather events that could cause mass extinctions. c. it's an area that's an optimal distance from the sun for potentially supporting life. d. it's a region that's unaffected by asteroid or meteor impacts.

Why are there increasing problems with construction in permafrost regions? a. the existence of black spruce trees b. global warming c. booming arctic populations d. longer freeze-thaw cycles