John likes walking in the open air on weekends, _______. [ ]

Now the air in our city is ______ than it used to be. Something must be done to stop it.

______ difficult it is, he is determined to ______ the experiment.

Of all your coats, why do you like this one best?—Because it’s _________ than the others.

Wow, my new bike looks the same as ___________. ——–Really.