There is an obvious _______ between children spending too much time playing computer games and their bad grades at school. 

What the expert has said and done will be _______ to the department managers.

Many people like white color as it is a ________ of purity.

Many scientists have believed that there may be a _________of life on the Mar．

 ---What _______ do you have for Daniel?--- I think he should study harder than before.