Covalent bonds usually form at room temperature

Its either a) or b),wind and water erosion gradually widen the canyon

Iam not sure but to me it with be a or dsorry if i was late! hope this ! : )if you really want me to find out the answer that is correct tell me and i will do more research but the a or d makes sense to me.

We are not able to see the stars. light prevents our seeing the stars. i hope it kinda : )