Step-by-step explanation:
Let's read the instructions. There are 20 people at a party.
Let's visualize this. The letter 'P' stands for every person at a party.
PPPPPPPPPPPPPPPPPPPP
Let's continue reading. Most of them don't want to have desert.
Let's visualize this again. The bolded 'P' stands for what we think are people that don't want to have desert. Since the description says 'most', let's go with 15 people who don't want to have desert.
PPPPPPPPPPPPPPPPPPPP
Now the problem reads, how many people WANT to have desert? Since most people want to not have desert, there should be a few amount that wants desert.
A: Could be correct, but the key term in this problem is 'most'. 9 people wanting desert vs 11 people not wanting desert. 11 is not MOST PEOPLE.
B: Most of the people don't want desert so there can't be more people wanting desert and not wanting desert, so this is wrong.
C: Problem directly said most doesn't want desert, which means the number is not split off, so this is wrong.
D: This is correct, because since 'most' of them don't want desert, the lowercased amount of 'P' is very small.
D is your correct answer.