When you are looking at a work by Monet, stand back at least fifteen or twenty feet.

simple, compound, complex, compound-complex

complex

Right.

The sentence "When you are looking at a work by Monet, stand back at least fifteen or twenty feet" is a complex sentence.

To identify the sentence structure, we can break it down into its components:

1. Dependent clause: "When you are looking at a work by Monet"
- This clause begins with the subordinating conjunction "When" and depends on the main clause to make complete sense.

2. Independent clause: "stand back at least fifteen or twenty feet"
- This clause can stand alone as a complete sentence because it contains a subject ("you") and a verb ("stand back").

Since the sentence contains an independent clause and a dependent clause, it is classified as a complex sentence.