input: OPTIONS:
- per arable land
- number per household
- arable land per capita
- number per area Now, answer this question: Q: How is population density expressed? A:
A:
output: number per area

input: OPTIONS:
- progesterone
- gastrin
- oxygen
- secretin Now, answer this question: Q: The entry of acidic chyme into the duodenum stimulates the release of what? A:
A:
output: secretin

input: OPTIONS:
- mosses
- trees
- fungi
- bacteria Now, answer this question: Q: What were the first photosynthetic organisms on earth? A:
A:
output:
bacteria