Ans: (D)
Question: What must a chemical reaction overcome before starting?
Options:
- (A) PV=nRT
- (B) heat or cold
- (C) reactants
- (D) energy barrier
- (E) Dehydration
- (F) harmful substances
- (G) resistance
- (H) temperature
CoT: All chemical reactions require activation energy to get started. Activation energy is required to overcome the energy barrier. All chemical reactions must first overcome the energy barrier.

Ans: (E)
Question: Animals that tend to have complex nervous systems are missing what?
Options:
- (A) Energy
- (B) Energy.
- (C) nervous system
- (D) Chlorophyll
- (E) backbone
- (F) alleles
- (G) abdomen
- (H) brain
CoT: Most invertebrates have a more complex nervous system. Invertebrates are animals without a backbone. Most animals without a backbone have a more complex nervous system.

Ans: (H)
Question: What is it called when an animal divides into two parts?
Options:
- (A) limb amputation
- (B) The bending of a ray of light
- (C) Veins and arteries.
- (D) epidermis and dermis
- (E) the body's largest organ
- (F) Leptospirosis
- (G) refraction of light
- (H) asexual reproduction
CoT: Fission takes place when an animal divides into two parts. Asexual reproduction is by fragmentation, budding, or fission. Asexual reproduction is when an animal divides into two parts.

Ans: (C)
Question: What kind of animals conserve energy with their hair or fur?
Options:
- (A) fur
- (B) bears
- (C) mammals
- (D) sweating
- (E) frogs
- (F) cactus
- (G) goats
- (H) humans
CoT: Mammals conserve body heat with their hair or fur. Basically, heat is energy. Mammals conserve energy with their hair or fur.