Grain is stored in a silo, so this analogy needs a word that describes a place in which wealth is stored. Abstractly speaking, there are many options for this, for people “store” wealth in stocks, gold, paintings, and many other things. Luckily, none of the answers are tempting in this way, for the others are variously related to wealth but not as places for storage. Only the humble word “bank” fits that usage.

A "trinket" is a small item of little value. The word can describe either jewelry of this type or small items that might be set out as a humble ornament (like a small porcelain statue or something of that sort). Such trinkets can be placed on a shelf, and this makes the most sense among the possible sense of this analogy, given the potential answers. We can say that just as a trinket is placed on a shelf, so too can a tool be placed in a belt. (There are tool belts used by people working with tools.)

A "ship" is docked in a "port," while a "car" is parked in a "garage."

A sheathe is the covering into which a sword is placed. You have likely seen this in movies that depict knights and warriors. The sheathe is often on the belt of the warrior, and he will place the sword into the sheathe after having used the blade. The analogy could be read, “Just a sheathe is used to cover a sword, so is a veil used to cover a X.” A veil is the covering that is used by women to hide their faces, often for events like weddings. A veil also can be just any type of cloth used to hide something from sight; however, among the options provided, only face stands in relation to veil like sword does to sheathe.

An "aquarium" is designed to contain "fish," just as a "terrarium" is designed to contain "plants."