3. My old phone is _____, but I'd like to get a new one. a awesome b OK c all right

The adjective that does NOT fit in sentence 3 is a awesome.

Explanation: The sentence implies the phone is not good enough, hence the desire for a new one. 'Awesome' is a strongly positive adjective and contradicts this. 'OK' and 'all right' suggest mediocrity, which fits the context of wanting a new phone.

Answer: a awesome