the front door ___ ,he had to enter the room through the back door.

When a friend of mine comes _____ difficulties, I will give him or her my hand the first time

Nowadays, many people______ the theory that acupuncture is related to the production of chemicals in the body which reduce pain.

He wrote a letter ______ he explains what had happened in the accident.

My parents, with me __________ taking a walk in the park.