Opinion because they’re deciding what to do
"I am still a beast at bay," he said, in a low, hoarse voice. "Get ready, General Zaroff."
An impression means that there is an opinion taking place, and is often not what you would call facts.
1. Almost bizarre quality about the general's face.
One is opinionated, Rainsford finding him to be bizarre. It cannot be considered anything other than an impression because finding something to be weird is not something every person can agree on. This is an impression Rainsford had from the actions General Zaroff took.
4. The face of an aristocrat
Similarly, number four is also opinionated. There is no real "face" to an aristocrat, and so the line merely implies that Rainsford felt as if with a face like that, General Zaroff could be an aristocrat. This means that this one is also an impression Rainsford had been able to draw from observing him.
Numbers two, three, five, and six are not the correct answer. These answer choices do not provide an impression, and instead explain what is happening in a scene. Anybody in a room would be able to agree that the Cossack had put away his pistol, and that the general had turned to him and made a sign. Numbers two and three are both describing how General Zaroff looks, and although it seems a bit personally detailed, anybody would be able to look at his face and point out that Zaroff has thick eyebrows, black hair, and dark eyes.
This is why the only applicable choices would be one and four.
The best answer to this question would be, "Whom would you like to invite to the party?". Whom is an objective pronoun.
