Final answer:
To punctuate the sentence correctly, include apostrophes to show contractions and possession: "We're wondering who'll buy Mrs. Fox's house across the street."
Step-by-step explanation:
Punctuation is the tool that allows us to organize our thoughts and make it easier to review and share our ideas. The standard English punctuation is as follows: period, comma, apostrophe, quotation, question, exclamation, brackets, braces, parenthesis, dash, hyphen, ellipsis, colon, semicolon.
The sentence "We're wondering who'll buy Mrs. Fox's house across the street." should be punctuated with an apostrophe in We're to represent the contraction of "We are," and in who'll to signify the contraction of "who will." Additionally, Mrs. Fox's house needs an apostrophe to show possession, indicating that the house belongs to Mrs. Fox.