question... What causes the penis to develop?
Options:
- (A) Creatine
- (B) Energy
- (C) Estrogen
- (D) Testicles
- (E) matter vibrating
- (F) Testosterone
- (G) movement
- (H) It expands
answer... Testosterone stimulates the reproductive organs to develop into male organs. Male mammals have a tube-like organ called the 'penis'. Testosterone causes the penis to develop.
The answer is (F)

question... What has a layer of fat under the skin to help insulate the body?
Options:
- (A) goats
- (B) snakes
- (C) hamburgers
- (D) animals
- (E) humans
- (F) rabbit
- (G) bears
- (H) fur
answer... Mammals have a layer of fat under the skin to help insulate the body. All humans are mammals. Humans have a layer of fat under the skin to help insulate the body.
The answer is (E)

question... _ are tetrapods.
Options:
- (A) animals
- (B) amoeba
- (C) Frogs
- (D) Length
- (E) insects
- (F) Spiders
- (G) Snakes
- (H) Birds
answer...
Amphibians are the first true tetrapods, or vertebrates with four limbs. Frogs are classified as amphibians. Frogs are tetrapods.
The answer is (C)