May be if I ______ science, and not literature then, I would be able to give your more help.
| A．had studied | B．would study | C．studied | D．was studying |
Toni Morrison, Nobel Prize-winning American writer, says if there’s a book you really want to read, but it ______ yet, then you must write it.
| A．hasn’t been written | B．hasn’t written | C．doesn’t write | D．isn’t written |
It is believed that forest bathing ______ strengthen the immune system.
| A．should | B．must | C．need | D．can |
As long as the laws of nature ______, there will be tornadoes.
| A．exist | B．are existing | C．will exist | D．existed |
North Korea fired a long-range rocket last month, but the launch was reported ______ in failure.
| A．to end | B．to have ended | C．having ended | D．ending |
Some scientists have questioned the theory ______ CO2 is causing dangerous global warming.
| A．which | B．what | C．that | D．why |