which of the following things can you not write with?\no la pluma\no la luz\no el bolígrafo\no el lápiz

Brief Explanations:

"la pluma" means pen, "el bolígrafo" means ball - point pen, "el lápiz" means pencil, all of which can be used for writing. "la luz" means light, and light cannot be used for writing.

Answer:

B. la luz