Identify the type of sentence.

After the supplies are delivered, we will decorate the room.

simple sentence

compound sentence

complex sentence

compound-complex

The sentence above is a complex sentence.

Explanation:

A complex sentence has at least one independent clause and one dependent clause. The difference between an independent clause and a dependent one is that the former can stand alone as a sentence because it represents a complete thought (2). On the contrary, dependent clauses are dependent on the main sentence to complete their meaning, so they fail so stand alone as a sentence (see 1).

1) * After the supplies are delivered

2) We will decorate the room