Question 1

正确答案： 20 balloons|20 BALLOONS   

Question 2

正确答案： units of measurement/measurements/measurement units|units of measurement|measurements|measurement units|UNITS OF MEASUREMENT|MEASUREMENTS|MEASUREMENT UNITS   

Question 3

正确答案： rock salt/salt|rock salt|salt|ROCK SALT|SALT   

Question 4

正确答案： crystals|CRYSTALS   

Question 5

正确答案： string/piece of string|string|piece of string|STRING|PIECE OF STRING   

Question 6

正确答案： (ordinary) (white) light|ordinary white light|light|white light|ordinary light|ORDINARY WHITE LIGHT|LIGHT|ORDINARY LIGHT|WHITE LIGHT   

Question 7

正确答案： h

Question 8

正确答案： b

Question 9

正确答案： e

Question 10

正确答案： c