The tracking party followed their prey to the river, but there they lost the trail, even though they had several bloodhounds with them.

What type of sentence is this?

a simple sentence

a complex sentence

a compound sentence

a compound-complex sentence

The answer to your question would be that the sentence above is a compound-complex sentence.

Explanation:

A compound complex sentence contains at least two independent clauses and at least one dependent clause. The dependent clause can be at the beginning, middle, or end of a compound complex sentence. You need to put a comma before the coordinating conjunction and another comma after the dependent clause when it is placed in initial position in the sentence.

1) The tracking party followed their prey to the river (independe clause)

2) But there they lost the trail (independent clause)

3) * Even though they had several bloodhounds with them (dependent clause)

The sentence The tracking party followed their prey to the river, but there they lost the trail, even though they had several bloodhounds with them is a compound-complex sentence.

Explanation:

Compound-complex sentences have at least two independent clauses joined by a conjunction - compound sentences - and at least one dependent or subordinate clause - complex sentence.

In the case of this sentence, the independent clauses joined by a conjunction would be The tracking party followed their prey to the river, but there they lost the trail, and the dependent clause would be even though they had several bloodhounds with them.