Some viruses live in a dormant state inside the body, and when ferns are dormant it is as if they are hibernating. Given these facts, what can stay hidden in a hibernating state inside the body among the following options: - infections  - blood cells  - fungi  - insects  - viruses  - honeybees  - plasma  - barnacles
viruses

Most mollusks have shells, and coral reefs and shells are made of calcium carbonate. Given these facts, what do mollusks contain among the following options: - harmful substances  - Organic compounds  - bacon  - cayenne  - acetic acid  - dogs  - Chlorophyll  - Calcium carbonate
Calcium carbonate

Q: Erosion causes a river to become deeper and wider, and weathering and erosion continue to shape it today. Given these facts, weathering causes what to become deeper and wider among the following options: - a landslide  - Sediment  - a mountain  - a volcano  - soils  - rock  - flooding  - a river
A: a river

Question: Electricity sometimes is used for heating buildings, and hospitals incorporate most types of technical systems encountered in other types of buildings. Given these facts, what is electricity sometimes used to heat among the following options: - space  - hospitals  - waves  - direct energy  - energy  - Light  - condensation  - clouds
Answer: hospitals

*Question*
Cold fronts cause thunderstorms as they pass by, and if cold air is advancing on warm air, the front is called a cold front. Given these facts, which situation can cause a thunderstorm among the following options: - Fog rising over a lake  - pressure differences.  - Earth's axis of rotation is tilted  - Setting up lightning rods  - Cold air advancing on cold air  - Cold air advancing on warm air  - Changing the angle of the sun  - fall moving to winter
**Answer**
Cold air advancing on warm air

(Q).
Air pollution harms the respiratory and circulatory systems, and air pollution is caused by lots of different pollutants. Given these facts, what systems are pollutants bad for among the following options: - destroying life  - classification system  - an organism's body  - respiratory and circulatory  - animal habitats  - ambulatory systems  - social security system  - the environment
(A).

respiratory and circulatory