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

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


[Q]: Gravity makes soil and rock particles move gradually down the slope during each thaw.
[A]: What makes soil and rock particles move gradually down the slope during each thaw?


[Q]: Remember electrons are negatively charged, so ions with a positive charge have lost a(n) electron.
[A]:
Remember electrons are negatively charged, so ions with a positive charge have lost what?