Answer:
A. The Smithsonian is a large complex, for it has 19 museums, 9 research centers, multiple galleries, and a zoological park.
B. The Smithsonian is a large complex; it has 19 museums, 9 research centers, multiple galleries, and a zoological park.
C. The Smithsonian is a large complex; for example, it has 19 museums, 9 research centers, multiple galleries, and a zoological park.
Explanation:
There are only three acceptable ways to create a compound sentence:
A. by using a comma and a coordinating conjunction
B. by using a semicolon
C. by using a semicolon with a transitional expression