Answer:

Introduction:
In this question, we are given a sentence and we need to identify its type based on structure. The sentence is: "I left early so that I could get some work done, but I'll be back soon." Let's analyze the sentence and identify its type.

Sentence Analysis:
The given sentence consists of two clauses connected by the coordinating conjunction 'but'. Each clause has its own subject and verb. Let's break down the sentence:

- Clause 1: "I left early so that I could get some work done."
- Clause 2: "I'll be back soon."

Types of Sentences:
There are three main types of sentences based on structure: simple, compound, and complex.

Simple Sentence:
A simple sentence consists of a single independent clause, which means it has one subject and one verb. It expresses a complete thought. The given sentence does not fit the definition of a simple sentence because it contains two independent clauses connected by a coordinating conjunction.

Compound Sentence:
A compound sentence consists of two or more independent clauses connected by coordinating conjunctions like 'and', 'but', or 'or'. The given sentence fits the definition of a compound sentence since it has two independent clauses connected by the coordinating conjunction 'but'.

Complex Sentence:
A complex sentence consists of one independent clause and one or more dependent clauses. The given sentence does not contain any dependent clauses, so it does not fit the definition of a complex sentence.

Conclusion:
Based on the analysis, the given sentence "I left early so that I could get some work done, but I'll be back soon" is a compound sentence. It consists of two independent clauses connected by the coordinating conjunction 'but'.