How can I ever concentrate if you ________ continually ________ me with silly questions?

they are boys or girls, they should enjoy equal rights.[ ]

_____ twice a year, whether it is a car or a bus, is a rule that every driver must obey in this city.

Mr. Scott has received the invitation to his ex-girlfriend’s wedding ceremony this weekend. Will he attend it—No, he has finally decided _____.

___ difficult and challenging thetask may be, we must finish it on time, because there is a possibility _________we’llbe fired if we can’t fulfill the task on time．