After four years’ research, we now have a ______ better understanding of the disease.

I’m worn out,____,the bike doesn’t work well,___ I can’t go further.

Alan is a careful driver, but he drives ______ of my friends.

In my daily life I      ignore work , study , and other activities to check my phone for messages.

 The problem is not ____ so easy as you think. It’s far from being settled.