Which sentence contains an inappropriate shift in verb tense?

Question

Responses

Medicine continued to make remarkable advances in the 20th century, as technology entered the operating theater and new antibiotics became available.
Medicine continued to make remarkable advances in the 20th century, as technology entered the operating theater and new antibiotics became available.

Medicine makes remarkable advances in the 20th century, as technology entered the operating theater and new antibiotics become available.
Medicine makes remarkable advances in the 20th century, as technology entered the operating theater and new antibiotics become available.

Medicine continues to make remarkable advances as technology enters the operating theater and new antibiotics become available.
Medicine continues to make remarkable advances as technology enters the operating theater and new antibiotics become available.

Medicine made remarkable advances in the 20th century, as technology entered the operating theater, and new antibiotics became available.

Answer 1

Medicine made remarkable advances in the 20th century, as technology entered the operating theater, and new antibiotics became available.