I'm not very clear on the final bit in the sentence, "which a single is the best". I believed it is comparable to the clause in "I am intending to include the things they are", the purchase of object and the verb is reversed (I forgot what the grammatical expression https://odor-control-cat33332.goabroadblog.com/36382277/5-tips-about-odor-control-cat-you-can-use-today