There are two choices for us to make, one is to go on, and is to give up.

The researchers found clear and convincing evidence _________ happiness is the key when it comes to better health and longer lives.

He sent me an e-mail, _____ to get further information. [ ]

I don’t think there will be many studentsleft in the class，_______，because the conditions are notfit for studying

Jack is late again. It is ______ of him to keep others waiting.[ ]