They heard the news while they were having lunch.(when)

In a speech to high school students, a business owner makes the following statement short response

Which sentence has an adjective clause? a.mike rode his bike on mountain trails because he found them challenging.b.gary donated to charity whenever he could.c.liz,who could always make people laugh,was loved by the whole block.d.ever since adam was a little boy,he had his father in the fields

Which is it? the desert is than the mountains? 1. drier 2. more dry