How many times have you ________ to Shanghai ?
---Why didn’t you enjoy the talk?---It was __ _talk that I had ever listened to.
Frank often wears a mask _____ he can keep fit in the foggy and hazy (霾) weather.
They said they would have ____________ holiday.
We all want to try something new, but finding the _________ to start is always the hardest part.
---What do you think of the bridge?---I have never seen _________ before.