TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Stringed instruments can help show the relationship between tension and frequencies in strings.

SOLUTION: Stringed instruments can help show the relationship between tension and what in strings?

PROBLEM: Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as embryos.

SOLUTION: Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as what?

PROBLEM: Seedless and seed are the two divisions of vascular plants.

SOLUTION:
What are the two divisions of vascular plants?