Which of these is a mixture?
a. carbon
b. carbon dioxide
c. air
d. oxygen

i'm hoping this is like a multiple answer question. if it is then it would be, the location of the plants and also the height of the plants since one she wants to know where in her garden the chamomile grows best. but also to see which plants grew better in the location she also has to measure the plant itself. (if you can only choose one answer than it would be c).

i'm pretty sure it is letter c.) car