Lungs are used for breathing air by land animals, and inside of the lungs are little sacks called alveoli. Given these facts, what are used for breathing air by land animals among the following options: - Frogs - pigeons - gills - alveoli - fish - ferns - four limbs - water
alveoli

Mollusks reproduce sexually, and mollusks in the diorama include snails and clams. Given these facts, which of the following organisms would reproduce sexually and not asexually among the following options: - Flowers - plants - amoeba - bacteria - fungus - snail - fungi - insects
snail

Q: Rain causes erosion, and rain is also known as precipitation. Given these facts, what causes erosion among the following options: - rainfall - the Moon - precipitation - vehicles - ice wedging - Venus - Mars - mouth of rivers
A: precipitation

Question: Active immunity results when an immune response to a pathogen produces memory cells, and memory cells persist in the circulation for decades. Given these facts, what can persist in the circulation for decades among the following options: - active immunity - density - Veins and arteries. - oxygen cells - bacteria - chlorofluorocarbons - fur and fat - Chemical energy
Answer: active immunity

*Question*
Many consumers feed at more than one trophic level, and each step along a food chain is known as a trophic level. Given these facts, many consumers feed at more than one what along a food chain among the following options: - humans - cacti - goats - step - scale - Length - a path - Energy
**Answer**
step

(Question)
Muscle contraction occurs when muscle fibers get shorter, and movement is based on the contraction of muscles. Given these facts, what do muscle fibers need to do to enable movement among the following options: - Bend - strength - exercise - ligt - It expands - shorten - Vibrates - stay warm
(Answer)
shorten