Pick out the most effective word from the given words to fill in the blank to…

CONCEPT: In English, the particle that follows ‘beat’ fixes the phrasal verb’s meaning — the same base verb combined with different prepositions produces entirely different senses (striking out a rhythm, physically assaulting someone, radiating intense heat, or repelling an attack). To complete a fill-in-the-blank correctly, match the sentence’s specific situation to the ONE phrasal verb whose established meaning fits it.

APPLICATION: The sentence describes a swarm of wasps attacking you, and asks what is ‘not easy’ to do in response — that is, to successfully resist or repel that attack. The phrasal verb ‘beat off’ means exactly this: to force an attacker back or away by fighting or struggling, i.e. to repel or fend off an attack. ‘It is not easy to beat off a swarm of wasps if they attack you’ therefore means it is difficult to fend off the swarm once it attacks — which is exactly the situation described.

CROSS-CHECK — checking the other options:

• ‘out’ — ‘beat out’ means to produce a rhythmic sound by striking something, or to extinguish flames by beating at them — neither sense matches responding to an attack.

• ‘up’ — ‘beat up’ means to physically assault or injure someone through repeated blows — that describes attacking someone, not resisting an attack made on you, so it reverses the sentence’s intended meaning.

• ‘down’ — ‘beat down’ describes the sun radiating intense heat, rain falling hard, or forcing a price lower through haggling — none of these carry the sense of repelling an attacker.

RESULT: ‘off’ is the only offered option whose established meaning is ‘to repel/fend off an attack’, so it is the correct completion — ‘It is not easy to beat off a swarm of wasps if they attack you.’