Noun/adjective + preposition

The plan has been changed, but nobody seems to know the reason (a)   this.

Don´t ask me to decide. I´m not very good (a)   making decisions.

Some people say that Sue is unfriendly, but she´s always very nice (a)   me.

What do you think is the best solution (a)   the problem?

There has been a big increase (a)   the price of land recently.

He lives a rather lonely life. He doesn´t have much contact (a)   other people.

Paul is a keen photographer. He likes taking pictures (a)   people.

Michael got married (a)   a woman he met when he was studying at college.

He´s very brave. He´s not afraid (a)   anything.

I´m surprised (a)   the amount of traffic today. I didn´t think it would be so busy.