Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

A(n) gastropods is noted for having its eyes at the tips of stalks or tentacles that emerge from its head.
What type of creature is noted for having its eyes at the tips of stalks or tentacles that emerge from its head?

Most hormones are produced by the endocrine system.
Most hormones are produced by which human organ system?

The nucleus of an atom is positive due to the presence of positively charged protons.

What part of an atom is positive due to the presence of positively charged protons?