---social media but teenagers just them

What is the main idea of this paragraph

How to combine the two sentences in bold.

Which revision fixes the dangling modifier in this sentence? while reading a new mystery book, my dog curled up in my lap and slept. a.) curled up in my lap, my dog slept while reading a new mystery book. b.) while i was reading a new mystery book, my dog curled up in my lap and slept. c.) my dog, while reading a new mystery book, curled up in my lap and slept. d.) curling up in my lap while reading a new mystery book, my dog slept.