Final answer:
The provided sentence is correct, but adding a comma before the conjunction 'but' can improve clarity. Concision is also key in writing, so unnecessary words should be omitted for clarity and impact.
Step-by-step explanation:
The sentence "John had many job offers but he threw them all away." is grammatically correct and does not require any corrections regarding verb tenses or punctuation. However, we can add a comma before the coordinating conjunction for clarity: "John had many job offers, but he threw them all away."
When writing, it is essential to ensure sentences are both grammatically correct and clear to the reader. In this case, the use of a comma helps to separate the two independent clauses for better readability. Additionally, in academic writing, being concise is highly valued. Excess wordiness should be avoided to ensure clarity and effectiveness.
For improved writing, consider implementing the principles of concision and clarity: omit needless words and use punctuation to enhance the flow of ideas. This technique not only makes the sentence easier to read but also more impactful.