There might be life on other planets, but so far scientists haven't found enough ________ to prove it.

 It came as a great _______ to the parents that their son finally came back safe and sound.  

They received a number of _____ from customers about the lack of parking facilities.

Dark clouds are a ___of rain while a smile a ____of friendship.

Scientists have achieved a major ___ in the search for a cure for cancer, ____ is good news for those who suffer from cancer.