What must you do to ensure that the code executes successfully?

Examine the following code:

The above code generates an error on execution.
What must you do to ensure that the code executes successfully?

A.
Use the TO_DATE function in line 2.

B.
Use the TO_DATE function in line 7.

C.
Use the TO_NUMBER function in line 6.

D.
Use both the TO_DATE function in line 2 and the TO_NUMBER function in line 6.

Explanation: