Which subordinate clause can be added to this independent clause?

i will be able to drive.
a. whereas i am eighteen years old.
b. rather than i am eighteen years old.
c. when i am eighteen years old.
d. unless i am eighteen years old.

Kwan gazed out at her brother and heard his shrieks of delight as he tried to direct their marvelous flying creation. she watched it wheel, spin, and dive—a wild, colorful bird putting on an aerial display. its gold and red crepe-paper wings fluttered in the air, mimicking the flight of a predatory bird surveying the landscape for prey. it swooped and dived, perhaps discovering a possible meal, and then went airborne again to avoid the rocky terrain below. min was the falconer, guiding his bird on its path through the sky, not yet ready to call it back to the ground. but kwan grew concerned when she looked out at the dark, threatening clouds beginning to roll in off the water. when she saw the streaks of lightning within the cloud formation, she pointed to the distant storm and called out to her little brother to bring in the kite. min nodded and rolled in the kite string, bringing his bird home. “let’s go,” kwan told her brother and put her arm around him to fold him safely under her wing as they both held onto the kite. “it’s time to go home.” how does the extended metaphor in paragraph 3 affect the mood of this passage? a-it creates a feeling of silliness that captures the absurd humor of the situation. b- it creates a sense of tranquility to match the feelings of min at this point. c-it creates a feeling of fear over what may happen if the kite crashes. d-it creates a sense of awe and wonder at min's mastery of the kite.