1. The correct answer is D, because there is no estimation or subjective opinion (such as "to my way of thinking", "pretty strong", "if you ask me"). The sentence is objective, and the only thing that allows for some relativity is the word "variety". However, the author would probably go on with explaining or concretizing this variety.
2. All of those phrases are powerful in terms of marketing, but I believe the correct answer is C. Lee wants to advertize the power and effectivity of this dishwasher, so he will most likely attract prospects by telling them that it is 100% guaranteed. "Key secrets" sounds too talkative for something as straightforward as a dishwasher; "money making" sounds ridiculous, as nobody expects to make money of a dishwasher. "Surprisingly simple" sounds a little bit out of place, as such a powerful dishwasher need not be that simple to attract us.