Definition and put them in a sentence

Tangible: Something you can touch. "The tension in the air was almost tangible."

Shrew: A small mammal that looks like a mouse, with a pointed nose and tiny eyes. Or an ill-tempered nagging woman (depending on the context)

"The shrew lived in a whole" or " That old shrew wouldn't stop complaining."

Regression: Returning to a less developed state. "You can blame unrest on economic regression."

Invariably: Always. "My schedule is invariably the same."

Introspective: Inward-looking. "He was withdrawn and introspective.

Naivete: Being naive. "His mistakes were due to his naivete."

Obscure: Not known about. Or to conceal. "His parents were obscure. or The clouds obscure the sun" (Depending on the context)

Cowered: Crouch down in fear. "The cat cowered in fear"

Spectre: A ghost or apparition. "He was sure he could see a spectre at the end of the hall."

Stimulus: Something that causes a reaction. "The stimulus caused her to kick her leg."

Explanation:

Hope this helps

a. is the correct answer