Identify sentence types: simple, compound, or complex.

To determine whether each sentence is a simple sentence (SS), a compound sentence (CS), or a complex sentence (Complex), we need to analyze the structure of each sentence:

Definitions:

1. Simple Sentence (SS): A sentence with one independent clause (a subject and a predicate that can stand alone as a complete thought).
2. Compound Sentence (CS): A sentence with two or more independent clauses joined by a coordinating conjunction (e.g., "and," "but," "so," "or," "nor," "for," "yet") or a semicolon.
3. Complex Sentence (Complex): A sentence with one independent clause and at least one dependent clause (a clause that cannot stand alone as a complete thought because it begins with a subordinating conjunction like "after," "because," "if," "since," etc.).

Analysis of Each Sentence:

1. The children wore their dirty boots.
- This sentence has one independent clause: "The children wore their dirty boots."
- Type: Simple Sentence (SS)

2. It was time for bed, yet it was still light outside.
- This sentence has two independent clauses: "It was time for bed" and "it was still light outside," joined by the coordinating conjunction "yet."
- Type: Compound Sentence (CS)

3. The front door was locked, so she entered through the back.
- This sentence has two independent clauses: "The front door was locked" and "she entered through the back," joined by the coordinating conjunction "so."
- Type: Compound Sentence (CS)

4. They took a lot of pictures when they visited Montana.
- This sentence has one independent clause: "They took a lot of pictures" and one dependent clause: "when they visited Montana."
- Type: Complex Sentence (Complex)

5. After the show began, he sat very quietly.
- This sentence has one independent clause: "he sat very quietly" and one dependent clause: "After the show began."
- Type: Complex Sentence (Complex)

6. The girl was wearing a red dress.
- This sentence has one independent clause: "The girl was wearing a red dress."
- Type: Simple Sentence (SS)

7. He was playing on his computer.
- This sentence has one independent clause: "He was playing on his computer."
- Type: Simple Sentence (SS)

8. Before the bell rings, the student lined up at the door.
- This sentence has one independent clause: "the student lined up at the door" and one dependent clause: "Before the bell rings."
- Type: Complex Sentence (Complex)

9. We turned off the lights.
- This sentence has one independent clause: "We turned off the lights."
- Type: Simple Sentence (SS)

10. We turned off the lights after our mom told us to go to sleep.
- This sentence has one independent clause: "We turned off the lights" and one dependent clause: "after our mom told us to go to sleep."
- Type: Complex Sentence (Complex)

Final Answer:

1. SS
2. CS
3. CS
4. Complex
5. Complex
6. SS
7. SS
8. Complex
9. SS
10. Complex

Boxed Answer:
\[
\boxed{
\text{SS, CS, CS, Complex, Complex, SS, SS, Complex, SS, Complex}
}
\]