Which letter in the diagram below represents the location where deoxygenated blood returns to the heart from the body?
-D
A-
с
B
ОА. В
B. C
C. D
D. A

What percentage of light hits earth's surface directly?

The wings of insects, birds, and bats evolved independently but carry out similar functions. this is an example of a. analogous structures. b. embryonic structures. c. vestigial structures. d. homologous structures.

Why do we perceive objects as retaining their brightness under different lighting levels?