The correct conjunction to complete the sentence is "so." This is because "so" is used to indicate a logical consequence or result. In this sentence, being tired is the reason for going to bed early.
The conjunction "but" is not correct because it is used to indicate a contrast or opposition between two ideas. "Yet" is not correct because it is used to indicate that an action or event has not happened, although it was expected or planned. The conjunction "or" is not correct because it is used to indicate a choice or alternative between two or more options.
Sentence
If your writing has been called "choppy" or "monotonous", the issue is usually sentence variety — not vocabulary. English readers expect a mix of short and long, simple and complex sentences. Even the same content reads completely differently depending on how you stitch the clauses together.
A sentence is the largest grammatical unit, made of one or more clauses. Four structural types: simple (one independent clause), compound (two+ independents joined), complex (independent + dependent), compound-complex (multiple of each). Ends with period, question mark, or exclamation mark.
Compound sentence
If you've ever been told you've written a "comma splice", you've hit the most common compound-sentence trap. The sun was shining, everyone appeared happy — looks fine, reads fine, but technically wrong. Once you can spot independent clauses, this error becomes obvious and easy to fix three different ways.
A compound sentence joins two or more independent clauses, each a complete thought. The link is a coordinating conjunction (and, but, or, so, yet) with a comma, or a semicolon on its own: I started on time, but I arrived late.
A2 | Elementary | Pre-intermediate
If you can order coffee, ask for directions, and tell someone what you did yesterday — but struggle the moment the conversation drifts into anything abstract — you're operating at A2. Knowing this matters: A2 is the level where most learners plateau because they reach for B2 material too early and burn out. Stay here and your foundations get unbreakable.
A2 is the elementary level in the CEFR framework, covering routine communication and the first wave of real grammar: past simple and continuous, present perfect, basic modal verbs, first conditional, and common verb-pattern rules.
Difficulty: Easy
If a textbook leaves you confused, sometimes the issue isn't the topic — it's that the practice material is layered with extra complications. Filtering by Easy strips that away. You get one rule at a time, in plain everyday language, with no trick questions. It's how you make a shaky foundation solid before stacking more on top.
The Easy difficulty tag marks beginner-level questions and challenges — typically A1 or early A2. Single-rule focus, short sentences, common vocabulary, one clear correct answer.