Carefully read the following sentences.

1. Ladybugs' markings are attractive to humans they are unattractive to predators.
2. Ladybugs' markings are attractive to humans but unattractive to predators.

Sentence 1 contains one or more errors. Which technique is used in sentence 2 to correct the grammatical problems in sentence 1?

A. adding a conjunction and rearranging phrases
B. inserting a semicolon
C. adding an independent clause
D. creating a subordinate clause

Please select the best answer from the choices provided