The boy was asked to read the sentences on the page. He started to read the first sentence and then the next sentence...There was a pause...The teacher said " _______"

1. Go ahead.
2. Go on.
3. Keep on.
4. Keep on reading.

(Can we use all the expressions in the blank? Which ones are commonly used?)

All can be used. In my experience, "go ahead" or "go on" might be used more often than "keep..."

Yes, all of the expressions can be used in the blank depending on the context and the speaker's preference. However, some expressions are more commonly used than others.

1. "Go ahead" is commonly used to give someone permission or encouragement to continue with a particular action. In this case, the teacher would be telling the boy to continue reading.

2. "Go on" is similar to "go ahead" and is also commonly used to tell someone to continue with what they were doing. It is a simple and direct way of encouraging the boy to continue reading.

3. "Keep on" is also commonly used to encourage someone to continue with a task or activity. However, it is slightly less common than "go ahead" or "go on."

4. "Keep on reading" is a specific instruction to continue reading. It is often used when someone interrupts their reading or pauses for a moment. The teacher might use this expression to indicate that the boy should keep reading without stopping.

In conclusion, all of the expressions can be used in the blank, but "go ahead," "go on," and "keep on reading" are the most commonly used ones.