Both minutes and hours are units of time, with a minute being shorter than an hour. So, we need to look for an answer choice in which the first word depicts a shorter length of time than the second word. Thus, the best answer choice is "century is to millennium" because there are multiple centuries in one millennium!

Since handlebars are the part of a bicycle which one uses to steer it, we need to pick out an answer choice that describes the part of a car used to steer it. While all the answer choices are nouns that represent parts of a car, "steering wheel" is the correct answer because one uses a car's steering wheel to steer it, just like one uses a bicycle's handlebars to steer it.

Months are smaller divisions of a year, so to solve the analogy, you need to pick out an answer choice in which the first answer is a smaller division of the second answer. Seconds are smaller divisions of a minute just as months are smaller divisions of a year, so "second is to minute" is the correct answer. Considering the other answer choices, a baby "cow" is called a "calf" and "cows" give birth to "calves," a "child" develops into an "adult," "sage" and "page" are words that rhyme, and "noise" and "silence" are opposites, so none of the other answer choices are related in the same way that "month" is related to "year."

When riding a bicycle, one uses the handlebars to steer, so we need to pick out an answer choice that describes which part of a car one uses to steer when driving it. One uses the steering wheel of a car to steer it, just as one uses the handlebars of a bicycle to steer it, so “steering wheel” is the correct answer.

Snakes are covered by scales, so to solve this analogy, you need to pick out an answer choice that describes what covers trees. Many trees are covered by bark, so "bark" is the correct answer.

"Claws" grow from the digits of a "bear," just as "nails" grow from the fingers of a "man."

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.