What are the requirements for an S corporation?

The corporation must be a domestic corporation and not be a member of an affiliated group of corporations; the shareholders must be individuals, estates, or certain trusts and tax$-$exempt organizations; there may be no more than $100$ shareholders; the corporation must have only one class of stock; and no shareholder may be a nonresident alien.

The corporation must be a domestic corporation and not be a member of an affiliated group of corporations; the shareholders must be individuals, estates, or certain trusts and tax$-$exempt organizations; there may be no more than one hundred shareholders; the corporation must have only two classes of stock; and no shareholder may be a nonresident alien.

The corporation must be an alien corporation and not be a member of an affiliated group of corporations; the shareholders must be individuals, estates, or certain trusts and tax$-$exempt organizations; there may be no more than $100$ shareholders; the corporation must have only one class of stock; and no shareholder may be a nonresident alien.

The corporation must be a domestic corporation and not be a member of an affiliated group of corporations; the shareholders must be individuals, estates, or certain trusts and tax$-$exempt organizations; there may be no more than $1000$ shareholders; the corporation must have only one class of stock; and no shareholder may be a nonresident alien.