21. which statement is true about a nucleus?
a. it is the site of enzyme storage.
b. it is the site of energy conversion.
c. it is surrounded by antibodies.
d. it is surrounded by a double membrane.

Answer:

D because when the eukaryotic cells consumed the prokaryotic cells it (prokaryotic cells) came with a membrane so now it has a double membrane

one part of the electromagnetic spectrum that arrives on earth as solar radiation from the sun is the visible spectrum. wavelengths of the visible spectrum combine to form what we refer to as

answer - d) ultraviolet radiation.

violet /   380–450 nm / 668–789 thz

violet is number 1 in the chart of visible light.