There are a number of cases _______ family members or friends quarrel with each other and become enemies.

I think natural wonders are more interesting than man-made ________.

The most successful retired athletes are those who can ____ the life skills they learned in sports to another area of life.

More expressways in Sichuan soon to promote the local economy.

Tom _________ Mary in 1998. That is to say, they _________ for 12 years.