Questions & Answers about We zagen de hindernis, wat een groot probleem was.
Why use wat instead of die when hindernis is a de-word?
Usually, you would use die to refer back to a de-word like de hindernis. However, in this sentence, wat doesn't refer to just the obstacle itself. Instead, it refers to the entire preceding clause. It means the whole event—the fact that we saw the obstacle—was a big problem.
What if I wanted to say the obstacle itself was the problem?
Then you would use die to refer specifically to de hindernis, resulting in: We zagen de hindernis, die een groot probleem was. That changes the meaning to focus purely on the obstacle being the problem, rather than the situation of seeing it.
Could I use dat to refer to the whole sentence instead?
No. When referring back to a complete sentence or clause in Dutch, you must always use wat. The relative pronoun dat is strictly used to refer back to specific het-words.
Why is the verb was pushed to the very end of the sentence?
The phrase starting with wat is a relative clause, which means it acts as a subordinate clause. In Dutch subordinate clauses, the conjugated verb (in this case, was) is always moved to the end.