Which sentence effectively combines the clauses to make Clause 1 dependent on Clause 2?

Clause 1: Padmi looks frantically for her pen

Clause 2: her sister calmly writes with it

Question 9 options:

Padmi looks frantically for her pen. Her sister calmly writes with it.

Padmi looks frantically for her pen, and her sister calmly writes with it.

While Padmi looks frantically for her pen, her sister calmly writes with it.

Padmi looks frantically for her pen; her sister calmly writes with it.