(question). Where do organisms cluster on the ocean floor?
Options:
- (A) neutralized water
- (B) where they used to live
- (C) hot alkaline water
- (D) fissures of hot, acidic water
- (E) sedimentary rocks
- (F) fissures blasting cold water
- (G) at or near the margins
- (H) an area swollen with pus
(answer). Organisms cluster around hydrothermal vents in the ocean floor. Hydrothermal vents are fissures in the ocean floor that leak hot, acidic water. Organisms cluster around fissures in the ocean floor that leak hot, acidic water.
The answer is (D)

(question). Which type of system do most animals without backbones have?
Options:
- (A) sensory neurons
- (B) Veins and arteries.
- (C) Nervous system
- (D) Stereo system
- (E) Root system
- (F) to move people
- (G) Skeletal system
- (H) insects
(answer). Most invertebrates have a nervous system. Invertebrates are animals without a backbone. Most animals without backbones have a nervous system.
The answer is (C)

(question). Mutation leads to _.
Options:
- (A) Devolution
- (B) Plants growth
- (C) rapid expansion
- (D) Evolution.
- (E) Degeneration
- (F) Extinction
- (G) massive damage
- (H) anemia
(answer). Mutation creates new genetic variation in a gene pool. Genetic variation is the raw material for evolution. Mutation leads to evolution.
The answer is (D)

(question). Carbon monoxide, a product of furnaces and engines, is a:
Options:
- (A) acid
- (B) CO2
- (C) kill
- (D) harm
- (E) gas
- (F) form
- (G) CO 2
- (H) HPV
(answer).
Carbon monoxide is a gas produced by furnaces and other devices that burn fuel. Fuel is burned inside the engine. Carbon monoxide is a gas produced by furnaces and other engines.
The answer is (E)