The dense fluid in chloroplasts where carbon dioxide is converted to sugar is called the
a. thylakoid
b. stroma
c. grana
d. stomata

The correct answer is b. stroma.

Chloroplast is a cell organelle, present in the green plant cells. It is surrounded by two membranes outer and inner membrane. Within the inner membrane, dense fluid or matrix or ground substance is present which is called stroma. It is alkaline aqueous fluid, rich in protein. It contains enzymes for reduction of the carbon dioxide into sugar (carbohydrate). Chloroplasts also have a third internal membrane called the thylakoid membrane, which contains chlorophyll molecules.