Breakdown of Кто тот гений, который изобрёл этот прибор?
кто
who / whoever
этот
this [f: эта, n: это]
тот
that
который
which / who / that (relative pronoun)
Questions & Answers about Кто тот гений, который изобрёл этот прибор?
Why is который used in this exact form?
The relative pronoun который must match the gender and number of the noun it refers back to. Here, it refers to гений (genius), which is masculine singular. It is in the Nominative case because it acts as the subject of the second half of the sentence (the person who invented).
Why do we use both тот and этот in the same sentence?
They mean different things based on distance! Тот means "that" (pointing to something further away or more abstract), which is why we say тот гений (that genius). Этот means "this" (pointing to something close by), giving us этот прибор (this device).
If прибор is the thing being invented, shouldn't it change its ending for the Accusative case?
It is actually in the Accusative case here! Because прибор (device) is an inanimate masculine noun, its Accusative form looks exactly the same as its dictionary (Nominative) form. That is why the phrase этот прибор does not change its spelling as a direct object.
The verb изобрёл looks unusual. What is its dictionary form?
The infinitive is изобрести (to invent). It is a perfective verb with an irregular past tense. Since the subject of that action is который (referring to the masculine noun гений), the verb takes the masculine past tense form изобрёл.