Final answer:
The sentence 'You must reach there__week-end.' should likely include 'by the' before 'week-end' to indicate a deadline for arrival, based on similar contextual usage found in different texts.
Step-by-step explanation:
The sentence 'You must reach there__week-end.' appears to have a missing word before 'week-end' that provides context to the time frame in which someone must arrive at a destination. The appropriate word to fill in the blank could be 'by the', which indicates a deadline for arrival.
Let's look at similar examples from various texts to understand how 'week' and related time expressions are used in context: All is over with him, by this time, thought I at last, when through another week no further intelligence reached me. On seeing her boss's non-verbal reaction Jane thinks "Oh, I guess that didn't go too well. She/he really wants me to finish this project by the end of the week.
It was three o'clock when they attained their destination... Shortly after four o'clock the last remaining gun went out of action... the beleaguered possessed no further resources. The use of 'week' in various contexts typically refers to a period of time or a deadline. The phrase 'by the week-end' suggests that an action or event is expected to be completed before the weekend arrives.