Why? Ephemeral means lasting for a very short time.

Why? Benevolent (kind/well-meaning) is the opposite of malevolent (malicious).

Why? Abundant and plentiful both describe a large quantity.

Why? The present perfect takes "has" with the third person singular plus the past participle.

Why? A past action already in progress when another past action occurred uses the past continuous.

Why? With a third-person singular subject and a habitual time marker, the simple present "goes" is correct.