Are these sentence types correct?

Complex

While
scientists are studying past diseases such as the Spanish flu, they
constantly worry about the next pandemic to strike.

Compound
Various research facilities, such as the World Health Organization, are continually studying various new diseases, and tracking old diseases.

Compound-Complex
Because the W.H.O. continues to track older strands of the
influenza virus, it records the evolution of a virus, and may be the
first
to warn the world of a new disease.

3 answers

Your first sentence is labeled correctly.

A compound sentence has two independent clauses. The sentence you labeled as compound is a simple sentence.

The sentence you labeled compound- complex is a complex sentence. Compound-complex sentences have two independent clauses plus one or more dependent clauses.
thank you so much!!! i may post a few more in the next couple minutes to make sure those sentences are correct as well... THANK YOU!!!!
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