Answer:
B. They almost worked all day on the assignment.
Step-by-step explanation:
Modifiers are those words that are placed in a sentence so as to modify or change the frame of the sentence.
Misplaced modifiers are those modifiers that are placed/ used in a sentence but works in such a way that they modify other words rather than the intended word.
In the given sentence "they almost worked all day on the assignment", the modifier "almost" is used as a modifying word for the word "they" instead of the intended "worked". The emphasis will be on the word "work" rather than "they". The right sentence will read like "they worked almost all day on the assignment".
Thus, the sentence with the misplaced modifier is option B.