We must ______ known to all that smoking is harmful to heart.
| A．this | B．that | C．it | D．the matter |
Write clearly ____ your teacher can understand .you correctly.
| A．since | B．for | C．because | D．so that |
___we have satisfied you, you have no grounds of complaint.
| A．So | B．Since that | C．Now that | D．By now. |
Although, it's raining, ____are still working in the fields.
| A．they | B．but they | C．and they | D．so they |
Why these things happened was ____ the driver had been careless.
| A．because of | B．owing to | C．due to | D．that |
They had camped once before, ____ they knew what to take.
| A．because | B．now | C．so | D．since |