Which structure in leaves allows the gaseous reactants and products of photosynthesis to move in and out?

The correct answer is-  

Stoma allows the gaseous reactants and products of photosynthesis to move in and out.

Stoma ( plural stomata) are the tiny holes/ pores that are primarily found on the surface of leaf ( sometimes also presnt in stem) and help in the exchange of gases ( such as carbondioxide and oxygen, which are the gaseous reactants and products of photosynthesis respectively). They are surrounded by guard cells that regulate the opening and closing of stomata.

answer: i don't know

explanation:

you need to provide a picture, otherwise i can't tell you.

if you can provide one, i'd be more than happy to you with this!