Fill in: breathe, observing, repeat, separate,
struggle.
1. For this study, the psychologist will .......
the girls from the boys.
2. Although I .................. in physics, I do very well
in chemistry.
3. The air we................
is actually 78% nitrogen
and only 21% oxygen.
4. Scientists have to .................. their experiments
again and again to make sure the results are
valid.
5. Biologists have to be patient while they're ...........
animals in the wild.