Though ______, many laws of nature exist.
| A．not having been discovered | B．having not been discovered |
| C．not having discovered | D．having not discovered |
---It’s many years since I saw you last time. I _________ you at all.
---I wouldn’t have, either, if someone _________ you by the name.
| A．don’t recognize; hadn’t called |
| B．didn’t recognize; didn’t call |
| C．haven’t recognized; didn’t call |
| D．didn’t recognize; hadn’t called |
---When shall we meet your cousin at the station?
---His plane took off 2 hours ago, and it _________ arrive at 5pm.
| A．could | B．should | C．must | D．can |
Sometimes we buy a magazine with absolutely no purpose ________ to pass time.
| A．other than | B．rather than | C．more than | D．as if |
He is so addicted to smoking that ________ seems to be no chance of talking him into quitting.
| A．this | B．what | C．it | D．there' |
We’re expecting Jerry because he’s our _________ visitor who comes here for holiday every summer.
| A．familiar | B．regular | C．similar | D．popular |