Transient
(Select the word which means the opposite of the given word.)
a. Ephemeral
b. Harassing
c. Lasting
d. Jovial

Hint: Go through the given options and recall what they mean. The option which means the opposite or is the closest to meaning the opposite of the given word is the correct answer.

Complete answer: Antonyms are those words that express a meaning opposed to the meaning of another word, in which case the two words are antonyms of each other.
In the given question, the word ‘transient’ refers to ‘lasting a very short time’.
Let us analyze the options given to us in this question:
Option (a.), 'Ephemeral', refers to ‘lasting a very short time’.
Therefore, option (a.) is incorrect as its meaning is not antonymous to that of the given word ‘transient’.
Option (b.), ‘Harassing', refers to ‘annoy continually or chronically’.
Therefore, option (b.) is incorrect as its meaning is not antonymous to that of the given word ‘transient’.
Option (c.), ‘Lasting', refers to ‘existing for a long time’.
Therefore, option (c.) is correct as its meaning is antonymous to that of the given word ‘transient’.
Option (d.), ‘Jovial', refers to ‘full of or showing high-spirited merriment’.
Therefore, option (d.) is incorrect as its meaning is not antonymous to that of the given word ‘transient’.
Therefore, option c. is correct.

Note: Sometimes the given options in a question where we have to find the opposite of the given word do not exactly mean the opposite of the given word. If this happens, we have to select the option which is the most antonymous to the meaning of the word in the question.