Which option is an example of a complex sentence?
a. processed foods should be avoided because they can lead to serious health problems
b. processed foods are usually less expensive to purchase and easier to make
c. processed foods are a staple of the american diet
d. processed foods are very high in saturated fats and have very little nutritional value.

The answer is A. Processed foods should be avoided because they can lead to serious health problems

Explanation:

Complex sentences are the result of combining an independent clause and a dependent clause. An independent clause can stand by itself and includes a subject and verb; on the other hand, a clause is dependent if it relies on others to be complete.

From the options given the only one that includes these two types of clauses is option A as "Processed foods should be avoided" is independent and "they can lead to serious health problems" is dependent considering without the first sentence it is not possible to know that "they" refers to. Additionally, as in most complex sentences, the two clauses are linked by subordinating conjunction that in this case is "because" that links the two clauses but also shows the dependence relationship.

its repetition emphasizing that the chain is his own. sorry if i am wrong.