Once education is made free，many children who have dropped out of school .
| A．will come back | B．came back | C．have come back | D．had come back |
________ several times，but he still doesn't know how to do it correctly.
| A．Although I've taught him |
| B．I've taught him |
| C．Having been taught |
| D．Having taught |
Information technology is taught in most schools，________ we have entered the information era.
| A．so | B．while |
| C．for | D．still |
It's really very dangerous.One more step，________ the baby will fall into the well.
| A．or | B．so | C．but | D．and |
There is still much to discuss；________，we shall return to this topic at the next meeting.
| A．yet | B．therefore |
| C．otherwise | D．however |
Knowledge is the food of thought ________，as long as it is put in our brain，we will grow wiser.
| A．but | B．when | C．then | D．and |