Which statement distinguishes the light-dependent (l-d) reaction from the light-independent (l-ind) reaction?
a. the l-d reaction occurs in the thylakoid membrane and the l-ind reaction occurs in the stroma
b. the l-d reaction occurs in the cytoplasm and the l-ind reaction occurs in the chloroplast
c. the l-d reaction occurs in the chloroplast and the l-ind reaction occurs in the mitochondria
d. the l-d reaction occurs in the stroma and the l-ind reaction occurs in the cytoplasm

The correct answer is  (a).

Both L-D and L-IND reactions take place in the chloroplast of the cell but in different parts or locations. L-D reactions take place in the chloroplast thylakoids while L-IND reactions take place in the chloroplast stroma.

Chloroplasts are chlorophyll- filled organelles mostly found in the leaves of green plants.  Chloroplasts are surrounded by a double membrane called the thykaloid membrane that forms long folds within the organelle. In electron micrographs, the thykaloid membranes look like stacked coins. Chlorophyll is located within the thykaloid membranes.

Between the thykaloid  membrane and the chloroplast membrane is a space. This space is what is called the stroma.

1. is geographic distribution

2 is increasing complexity

3 is transitional forms