_____is a question scientists have yet to answer.

"I haven’t seen you for a long time".

"How_____ such an expensive dress?"

The people at the party were worried about Janet because no one was aware_____ she had gone.

_____ in large quantities is not necessarily an indication of its quality.

"Do you know Don Kline?"

"I remember the name but I can't remember_____"?

The function of "That clause" in "The basis for this American custom is that most parents teach their children_____"

Is this_____ you asked him for?

"Call the restaurant and ask for that information"

"I don't remember_____"

They always give the available seats to _____ comes first.

"Why doesn't Kurt get his hair cut?"

"I don’t know_____"

"The postal strike started today"

"_____something to prevent it?"

Scientists are attempting to find out_____ there is life on other planets.

Punish_____ is late.

Because of the rain, people are calling to ask_____ take place.

"Why did you talk to the teacher after class?"

"I didn't understand_____ during the lecture".

"I'm looking for the mail. Do you know_____?"

"Usually it comes by 4:00"