Under traditional (pre-Modigliani & Miller) capital structure theory, there is an assumed inverse relationship between WACC and company value. The idea is:
As a firm moves towards its optimal capital structure, the WACC falls, and the total value of the firm (equity
+ debt) rises.
Beyond that optimal point, extra gearing increases financial risk, so the required return from both debt and equity goes up, causing WACC to rise and firm value to fall.
So, within this framework, if a company's WACC increases, that means it has moved away from its optimal capital structure, and the value of the company will decrease.
Therefore, under traditional theory, an increase in WACC # decrease in company value, so the correct answer is B.

The company is repurchasing and cancelling its own shares.
When shares are cancelled:
Share capital is reduced by the nominal value of the shares bought back. # Any amount paid above nominal value reduces equity reserves (such as share premium and/or retained earnings), but it does not go through the Income Statement.
Total equity does decrease by the full repurchase amount (so option C is wrong).
No element of the repurchase (including any "premium to market value") is treated as an expense in the Income Statement under IFRS - it's purely an equity transaction (so D is wrong).
Option A is too specific and not strictly correct, because the premium over nominal is not necessarily all charged only to retained earnings - it can also be charged to share premium / other reserves.
So the one fully correct statement is:
B). The share capital figure would reduce by the nominal value of the shares purchased.

A buyback is appropriate when the company has a one-off cash surplus and no good investment opportunities.