"He looked around, and his eyes fell on the face of the squad leader, who had marched along with the last five."- pg. 43
This quote contains personification, as Alex used this to enhance the meaning of him looking at the squad leader. The author gave his eyes personification. Falling is a human action, and eyes can't fall. Alex gave his eyes this personification so that the reader can understand that he glanced at the squad leader fast. The personification also makes the reading more interesting, as it is more amusing and creative for the reader not to get bored.
This simile is used to demonstrate how fine the snow is, and how firm the drifts were. Without this simile, the reader wouldn't be able to understand how fine it is, or how firm it is. If Alex only says the object is hard, the reader might think variations of things and shapes. With a simile, the reader can clearly imagine how the object feels like or looks like.
This line demonstrates an onomatopeia because "H'm" represents a sound made by Tiurin. This gives the reader the sensation of being in the middle of the conversation, as people make sounds like that when they are talking.