【正确答案】 D

【答案解析】You are given that r=-2. Therefore, the best approach to solving this problem is to replace r with-2 in each of the answer choices, as follows:
Answer choice A: 4pr²=4p(-2)², which equals (4)(4)p, or 16p.
Answer choice B: 2pr³=2p(-2)³, which equals (2)(-8)p, or -16p.
Answer choice C: -2pr⁴=-2p(-2)4, which equals (-2)(16)p,
or -32p.
Answer choice D: -4pr⁵=-4p(-2)⁵, which equals (-4)(-32)p,
or 128p.
Answer choice E: -6pr⁶=-6p(-2)⁶, which equals (-6)(64)p,
or -384p.
The question asks for the least value. You are given that p＜0, which means that p is a negative number. If you substitute any negative number into the results obtained above, only answer choices A and D will yield a negative value. Therefore, you can eliminate answer choices B, C, and E, because they will all be larger than either answer choice A or D. When p＜0, 128p will always be less than 16p, so answer choice D is correct.
Alternatively, if you recognize that a negative number raised to an odd number remains negative, then only answer choice D will yield a negative number: -4×p (another negative number)×r⁵ (another negative number)=a negative number. All of the other answer choices would yield a positive number, so answer choice D must have the least value.