Choice "A" is correct. Generally, a person cannot pass on better title than the person has. However, if the owner of goods entrusts them to a merchant who deals in goods of that kind, and the merchant sells them in the ordinary course of the merchant's business, then the merchant has the power to transfer title to the goods. West was the owner of the clock and he entrusted the clock to Grill, who deals in new and used clocks. Grill sold the clock to Hone in the ordinary course of business. Thus, Grill had the power to pass on good title to the clock and did so when one of Grill's clerks mistakenly sold the clock to Hone. Because Hone has title to the clock, West cannot recover it from Hone. However, West does have an action for damages against Grill.
Choice "c" is incorrect. Although "c" gives the correct result, it is irrelevant whether or not the clerk was aware that the clock belonged to West.
Choice "b" is incorrect. As discussed above, a seller can convey better title than he has under the entrustment doctrine, which applies under the facts here.
Choice "d" is incorrect. It is irrelevant whether the clerk was negligent.