Scientists say it may be five or six years _____this medicine is tested on human beings.
A: since
B: efore
C: afte
D: when
A: since
B: efore
C: afte
D: when
举一反三
- Scientists say it may be five or ten years ________ it is possible to test this medicine on human patients.
- The Internet began its quick development since ______ . A: six years ago B: five years ago C: recently D: not mentioned
- When did the woman get the necklace（） A: Five years ago. B: Four years ago. C: Six years ago. D: Not long ago.
- Was it six years ago _______ we met for the first time? A: which B: When C: since D: that
- What is the theme of the story? ( ). A: Human beings are vulnerable in the nature. B: Human beings are superior to animals . C: Wolves are evil creatures that are dangerous to human beings. D: Human beings should treat animals like brothers with mutual respect.