Question

multiple choice
a semi - liquid substance surrounding the thylakoid membrane system.
a membrane system that contains chlorophyll.
an opening in plant leaves that allows gas exchange.
the fluid found inside of the thylakoid membranes.

Explanation:

The stroma in chloroplasts is a semi - liquid substance surrounding the thylakoid membrane system. The thylakoid membrane system contains chlorophyll. Stomata are the openings in plant leaves for gas exchange. The fluid inside thylakoid membranes is called the lumen.

Answer:

a semi - liquid substance surrounding the thylakoid membrane system.