I________all the cooking for my family，but recently I've been too busy to do it.
| A．will do | B．do |
| C．am doing | D．had done |
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 |
They studied what ______ since 2007 and found Australian electricity prices were among the highest in the developed world.
| A．has happened | B．happened | C．had happened | D．has been happening |