Learn Dutch: Wij wegen de mogelijkheden af en we praten erover. - We weigh the possibilities and we talk about them.

Because de mogelijkheden (the possibilities) is inanimate. In Dutch, you cannot use a preposition + a personal pronoun (like over ze) for things. Instead, you must use a pronominal adverb: er + over = erover. If you were talking about people, you would use over hen.

Why is the word af separated from wegen in the first clause?

The verb is afwegen (to weigh up / to consider), which is a separable verb. In a main clause in the present tense, the conjugated part (wegen) takes the second position, and the prefix (af) moves to the end of the clause.

Why does the sentence start with Wij but use we after the conjunction en?

Wij is the stressed pronoun, while we is unstressed. Starting with Wij puts a slight emphasis on who is taking the action. In the second clause, the focus shifts to the action itself, so the unstressed we is used to avoid sounding repetitive or overly emphatic.

What is the rule for forming the plural mogelijkheden from mogelijkheid?