Which of the following is a simple sentence?

A. Karen and David arrived at the airport at 3:35 p.m. and took a taxi to their hotel.

B. I went to the airport, but I was too late to meet them.

C. When I realized I was too late, I called David's cell phone and made arrangements to meet them in town.

D. I got to the airport late because the traffic was so terrible.

A is the simple sentence with a compound subject and compound verb.

subject Karen and David
predicate arrived and took

B. is a compound sentence, two sentences joined by "but"

C. and D are complex sentences.
When I realized..... is an adverb clause
because the traffic..... is also an adverb clause.

D is the simple sentence.

A look at the and
B see the comma...
C see the comma

The simple sentence among the options provided is D. "I got to the airport late because the traffic was so terrible."

To identify the simple sentence among the given options, we need to understand what a simple sentence is. A simple sentence is a sentence that consists of just one independent clause and expresses a complete thought.

Using this knowledge, we can examine the options to find the simple sentence.

Option A: "Karen and David arrived at the airport at 3:35 p.m. and took a taxi to their hotel."
This sentence consists of two independent clauses connected by the conjunction "and." Therefore, it is not a simple sentence.

Option B: "I went to the airport, but I was too late to meet them."
This sentence consists of two independent clauses connected by the conjunction "but." Therefore, it is not a simple sentence.

Option C: "When I realized I was too late, I called David's cell phone and made arrangements to meet them in town."
This sentence contains a dependent clause ("When I realized I was too late") and an independent clause ("I called David's cell phone and made arrangements to meet them in town"). Therefore, it is not a simple sentence.

Option D: "I got to the airport late because the traffic was so terrible."
This sentence consists of one independent clause and expresses a complete thought. Hence, this is the simple sentence among the given options.

Therefore, the correct answer is Option D: "I got to the airport late because the traffic was so terrible."