Concept:Identify the sentence with a grammatical or contextual error among four options.
Explanation:Option A: "Either my mother or my brother is cooking dinner."
This is correct. When two singular subjects are joined by "either...or", the verb is singular.
Option B: "This night we have an appointment at a big restaurant for a corporate meeting."
Here, "This night" is incorrect. The correct phrase is "Tonight".
Thus, the sentence should be: "Tonight we have an appointment at a big restaurant for a corporate meeting."
So, option B has a grammatical error.
Option C: "Newt Gingrich's America's Greatest Challenge serves as a rallying cry..."
The possessive "Gingrich's" and the title "America's Greatest Challenge" are correctly used, and the singular verb "serves" agrees. No error.
Option D: "Two gallons of water is too much to drink in a day."
"Two gallons" is treated as a single quantity, so the singular verb "is" is acceptable in standard usage. No error.
Only option B is incorrect. Options A, C, and D are correct.
Answer:Option B (or option 2).