Nouns that represent things that cannot be touched, heard or seen are known as

Abstract nouns.

For example, anxiety can not be touched, heard or seen but it is a whole inside oneself. Nor can anger, liberty, or democracy. It's there, but it is unseen.

it is believed to be alfred, lord himself

the answer is b. the tracer looks harmless in flight, but the pilot’s bitten lips and white knuckles suggest how dangerous it can be.