Any choices made when the ability resolves won’t have been made yet when it’s copied. Any such choices will be made separately when the copy resolves.

If the ability divides damage or distributes counters among a number of targets, the division and number of targets can’t be changed. If you choose new targets, you must choose the same number of targets.

If the ability is modal (that is, if it says, “Choose one —” or similar), the mode is copied and can’t be changed.

In some cases involving linked abilities, an ability requires information about “the exiled card.” When this happens, the ability gets multiple answers. If these answers are being used to determine the value of a variable, the sum is used. If an ability attempts to create a token that is a copy of “the exiled card,” it creates a token for each card exiled this way that is a copy of that card.

If the activated ability’s cost contains a choice, such as a creature to sacrifice or a number of counters to remove, the copy uses that same information. You can’t pay the cost again, even if you want to.

Verrak’s triggered ability creates another instance of that activated ability on the stack. It doesn’t cause any object to gain an ability.

If an ability is linked to a second ability, copies of that ability are also linked to that second ability. If the second ability refers to “the exiled card,” it refers to all cards exiled by the ability and the copy. For example, if Tidehollow Sculler’s enters-the-battlefield ability is copied and two cards are exiled, they both return when Tidehollow Sculler leaves the battlefield.

Activated abilities contain a colon. They’re generally written “[Cost]: [Effect].” Some keyword abilities (such as equip) are activated abilities and will have colons in their reminder text. An activated mana ability is one that produces mana as it resolves, not one that costs mana to activate.

The source of the copy is the same as the source of the original ability.