a problem can be solved, it must be obvious______the problem itself is

I didn’t hear you come in just now.— That’s good. We tried _____ any noise, for you were sleeping.

She was so ________ in her job that she didn’t hear anybody knocking at the door.

Owning pets has a positive influence on my life and I think animals __________our protection．

He asked who was able to ____ a good solution to this problem.