The original sentence is: "She cooked lunch then she cleaned the house."

To find the correct option, we need to identify the sequence of events. The original sentence indicates that cooking lunch happened first, followed by cleaning the house.

Let's analyze each option:

A. "Before she cooked lunch, she cleaned the house" - This suggests that cleaning the house happened first, which is not correct according to the original sentence.

B. "After she had cooked lunch, she cleaned the house" - This correctly indicates that cooking lunch happened first, followed by cleaning the house.

C. "She cooked lunch after she had cleaned the house" - This suggests that cleaning the house happened first, which is not correct according to the original sentence.

D. "She had cleaned the house before she cooked lunch" - This also suggests that cleaning the house happened first, which is not correct according to the original sentence.

Therefore, the correct option is:

B. After she had cooked lunch, she cleaned the house.