The sentence is describing an action that will have already taken place by a specific time in the future, the correct answer is will have started, as it is the future perfect form of the verb "to start" indicating that the action of starting the party will have already taken place by the time the speaker and the addressee arrive.
Present tense
If you've ever told someone I am living here for ten years (should be have lived or have been living) — you've hit the present perfect's main puzzle. English insists that "started in the past, still true now" lives in the present perfect, not the simple present. Internalise that one rule and a whole class of common errors disappears.
The present tense in English has four forms: simple present (I work) for habits and general truths; present progressive (I am working) for now or temporary; present perfect (I have worked) for past with present relevance; present perfect progressive (I have been working) for ongoing duration up to now.
Future tense
If you've ever wondered why a native speaker said I'm meeting her tomorrow instead of I will meet her tomorrow — you've felt the future-tense puzzle. English has at least four common ways to talk about the future, and they're not interchangeable. Pick the wrong one and you sound either unnaturally formal or surprisingly vague about your own plans.
English uses several constructions for future time: will + infinitive (predictions, spontaneous decisions: I'll call), be going to (planned intentions, evidence-based predictions: It's going to rain), the present continuous for arrangements (I'm meeting Sam at six), and the present simple for fixed schedules (The train leaves at 8).
B2 | Upper Intermediate
If a university admissions team or visa office has ever asked you for an English test score, B2 is probably the level they had in mind. It's the threshold where your English stops being a constraint and starts being a tool — and the line between B1 and B2 is often the line between "stuck in beginner classes" and "ready to study or work in English."
B2 is the upper-intermediate level in the CEFR framework, demanding flexible control of mixed conditionals, passive voice across tenses, reported speech with backshifting, and participle clauses.
Difficulty: Medium
If easy questions feel too obvious but hard questions leave you guessing, you're probably ready for Medium — the level where most real learning happens. It pushes just enough to expose the rules you don't quite have yet, without burying you in edge cases. This is where steady fluency is built, one well-aimed challenge at a time.
The Medium difficulty tag marks middle-range challenges — typically A2 to B1. One rule per question, realistic distractors, and contexts that require active thought rather than instant recognition.