Choose the correct answer.

This is Minh’s classroom. There are many things on the teacher’s desk. There is a blue marker and a whiteboard eraser. Minh likes the whiteboard because the teacher writes new words on it every day. On the desk, there is also a red crayon and a yellow glue stick. Minh’s favorite thing is the pencil sharpener because he can use it for his pencils. Next to the pencil sharpener is a green set square. The teacher uses it in Math class.

What color is the glue stick on the desk?