Final answer:
Contingent issuable shares are included in the calculation of diluted EPS only when it is probable that the conditions necessary for their issuance will be met. Therefore, the correct option is A.
Step-by-step explanation:
The condition that must be met to include contingent issuable shares in the calculation of diluted earnings per share (EPS) is that meeting the required condition is estimated to be probable (Option A). This means that for contingent shares to be included in the diluted EPS calculation, the financial or performance criteria that would result in the issuance of those shares must be likely to occur. If the achievement of the condition is considered probable, then the potential shares are treated as if they have been issued for the purposes of the diluted EPS calculation.