Breakdown of Weißt du, dass er das Kind abgeholt hat?
du
you (informal singular)
er
he
das Kind
the child
haben
to have
Questions & Answers about Weißt du, dass er das Kind abgeholt hat?
Why is hat at the very end of the sentence instead of right after er?
The word dass (that) is a subordinating conjunction. It introduces a dependent clause and forces the conjugated verb (here, hat) to move to the very end. Without dass, the normal order is Er hat das Kind abgeholt, but dass pushes hat behind the past participle abgeholt.
Why do we use weißt here for "know" instead of kennst?
Wissen (to know) is used for knowing facts or having information, which is exactly what a dass clause introduces. You use kennen when you are familiar with a person, place, or thing, such as if you were asking "Kennst du das Kind?" (Do you know the child?).
How is the past participle abgeholt formed?
The verb abholen (to pick up) is a separable verb, made of the prefix ab- and the verb holen. To form its past tense participle, the -ge- is sandwiched right in the middle, giving us ab-ge-holt.
Is the comma before dass required?
Yes, it is mandatory. In German grammar, you must always use a comma to separate the main clause (Weißt du) from the subordinate clause starting with dass. This is different from English, where we usually don't put a comma before "that".