A “guitar” is an instrument, and to play a guitar, you use its “strings." To solve this analogy, you have to determine which of the answer choices is something you use to play music on a “piano.” The correct answer is therefore “keys,” since the little black and white rectangles you press on to play notes on a piano are called “keys.” To provide further help, “percussion” is another name for the group of instruments played with sticks or by shaking them in a band or orchestra.

Door knobs help us to open doors, just like keys help us to open locks, so "key is to lock" is the correct answer.

Since waves are part of oceans, we need to pick out an answer in which the first thing is part of the second thing. While "birds are to nests" might seem like a good answer, because birds are found in nests, birds are not a part of nests, so "birds are to nests" can't be the right answer. "Branch is to tree" is the correct answer because a branch is a part of a tree, like waves are a part of an ocean.

A sail is part of a sailboat, so we need to pick out an answer choice in which the second word is a part of the first word. While "mop is to handle" and "bristles are to toothbrush" might each look like a potentially correct answer, a toothbrush is not a part of bristles, so "bristles are to toothbrush" cannot be the correct answer. A handle is part of a mop, however, just like a sail is part of a sailboat, so "handle is to mop" is the correct answer.

Hands have fingers attached to them, so to solve the analogy, you need to pick out the answer choice which describes the appendages attached to feet. So, "toes" is the correct answer.

The knee is a part of the leg that allows the leg to bend. So to solve this analogy you have to determine what whole thing the elbow is a part of. The correct answer is therefore "arm," because the elbow is a part of the arm that allows it to bend, just as the knee allowed the leg to bend.

Letters make up words, so to solve this analogy, you need to pick out the answer choice that describes something that words make up. Words make up sentences just as letters make up words, so "sentence" is the correct answer.

Individual letters must be combined to create words, which are gathered together into meaningful sentences. In the same manner, individual notes must be combined to create lines of music in a song. 

To complete the analogy, you first need to determine the relationship between the initial pairing. An "article" is a part of a "magazine." Therefore the answer must be in the form of "'whole' is to 'part.'" A "chapter" is a part of a book, so that must be the correct answer.

To complete the analogy, you first need to determine the relationship between the initial pairing. A "wheel" is a part of a car. Therefore the answer must be in the form of "'part' is to 'whole.'" A "garage" is a part of a house, so that must be the correct answer.