(Q).
If caves can be formed by carbonic acid in groundwater seeping through rock and dissolving limestone, then what is one element used to create caves? Answer choices: - sunlight - heat energy - Calcium carbonate - hydrogen and oxygen - calcite - carbonic acid - less water - salinity
(A).
carbonic acid

(Q).
If earth's orbital motion around the sun is key to the leaves of many trees changing colors, then what factor is instrumental behind the change of leaf colors during the year? Answer choices: - organisms and their habitat - global warming - Earth orbiting the Sun - Solar energy - scattered light - Greenhouse gases - Varying light output from sun - Moon orbiting the Earth
(A).
Earth orbiting the Sun

(Q).
If aplant requires nutrients for survival, then what does a plant require for survival? Answer choices: - offspring - nutrients - soul - Light - carbohydrates - Glucose - sunlight - humans
(A).
nutrients