Problem:OPTIONS:
- they bend
- It decreases
- It straightens
- permineralization
- It expands
- Damages them
- Localized damage
- Dehydration

Fact 1: Muscle contraction occurs when muscle fibers get shorter. Fact 2: Contraction of the muscle straightens the leg. Given the two facts above, what happens to your leg when muscle fibers shorten?
****
A: It straightens

Problem:OPTIONS:
- sex
- spring
- bird
- DNA
- ova
- production
- factories
- ovum

Fact 1: Reproduction is the process by which living things give rise to offspring. Fact 2: Physiologically, sex is for the purpose of reproduction. Given the two facts above, what gives rise to offspring?
****
A: sex

Problem:OPTIONS:
- sunlight
- tight soil
- Energy.
- loose soil
- Enzymes
- compacted roots
- energy
- compact soil

Fact 1: The looseness of soil has a positive impact on a plant 's roots' growth in that soil. Fact 2: Air exchange in the root zone is essential for root growth. Given the two facts above, what can enhance a plant's growth?
****
A: loose soil

Problem:OPTIONS:
- competing for resources
- competition
- A Greek letter
- heat or cold
- Earth orbiting the Sun
- permineralization
- bottleneck effect
- relocation

Fact 1: Bottleneck effect occurs when a population suddenly gets much smaller. Fact 2: Population is the number of people. Given the two facts above, what is it called when the number of people suddenly gets smaller?
****
A:
bottleneck effect