The conditions or circumstances surrounding something is called?

This device blocks an opening along the base/floor of stairs or other walking or working surfaces where materials or body parts might otherwise inadvertently fall through. it should be 4 inches high, with not more than ¼ inch clearance above the floor

Is the following statement true or false? the topic sentence of a paragraph should indicate what the paragraph is going to be about. false true

Why was kennedy concerned about the use of nuclear weapons