A part of the Calvin cycle has been removed from the diagram on the right. What occurs at this stage
of the cycle?

but there is no

i guess you forgot putting it.

the correct answer is option d.

an appositive is a noun, noun phrase or noun clause which follows another noun or noun phrase in order to describe it or name it another way. they are usually used between commas, brackets or dashes.

the example sentence with the correct use of commas is the following:

her uncle, the man over there in the red shirt, owns the hardware store in town.