Questions & Answers about Die Aktie, in die er investiert, ist sehr riskant.
Why is the relative pronoun in the accusative here (in die), instead of the dative (in der)?
The verb investieren takes the preposition in followed by the accusative case when you are talking about investing money into something. Because the noun it refers back to (die Aktie) is feminine, the accusative relative pronoun is die.
In English we often say "The share he is investing in". Can I put the preposition at the end of the clause in German too?
No. In German, a preposition that belongs to a relative pronoun must come immediately before it. You can never leave a preposition "dangling" at the end of a relative clause like you often do in English. It must be ...in die er investiert.
Does die Aktie just mean "share" in a general sense?
No, die Aktie specifically refers to a financial share or a stock in a company. If you mean a "share" in the sense of a portion or a contribution (like a share of a cake, or doing your share of the work), you would use a different word, like der Anteil.
Since we are learning about angenommen, dass (assuming that), how would I use it here to say: "Assuming that the share he is investing in is very risky, he could lose money"?