When Peter speaks in public, he always has trouble _ the right things to say.
New traffic rules that took effect on January l, 2013 are much stricter______ than in the past.
Rock climbing is ___ great fun. You will get close to ____ nature and take adventures at the same time.
— In order to improve your English, you need to practice more. — ______. Practice makes perfect.
How the fire in the dancing hall started _________ a mystery.
Please don’t try to back out _____ everything has been arranged.