Also, remember that we can't weaken a valid argument. If the conclusion is properly drawn, it is impossible to weaken it without changing the premises. So even before we weaken it, the question type has already precluded validity!
Correction: "Although the premises are false, the argument itself is valid since it can be inferred from the premises that Superman is indeed AN ACCOUNTANT"....
And thanks for adding the bit about soundness Cant Get Right*