Answer:
After passing her driving test, Lisa felt a sense of <u><em>lightness</em></u>.
Please <em><u>light</u></em> the candles on the birthday cake.
Patrick did not take the test <em><u>lightly</u></em> and studied intensely.
Explanation:
The words "light", "lightly" and "lightness" all signify a different aspect. "Light" is a verb while "lightly" is an adverb and "lightness" is a noun. And so, their uses are also all different, depending on the sentence structure.
In the first sentence, Lisa felt a sense of "lightness" after she passed her driving test. This means that she felt relieved.
The second sentence uses "light", asking someone to "light" the candle. This means that the candle must be made to burn.
The third sentence talks about Patrick not taking his test "lightly" which means that he is serious about it.
