You will be given a definition of a task first, then some input of the task.
You are given a passage. You need to construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is the whole paragraph. Avoid creating questions that can be answered correctly without actually understanding the paragraph.

unless the cracking is painful, it is not unusual or dangerous for your knees to "crack".

Lunges are excellent for strengthening the muscles around the knee joint. Make sure that you are not leaning over the knee, that the knee is right above the foot during the lunge and that you maintain a straight upright movement.

Do not do hamstring excercises that will pull on the knee joint if you have problems with your knee.

elipticals are good for running on with minimal knee and ankle stress.

you can also get large elastic bands...stand in them, and step out to the side pulling on the bands, then back in. Don't pull harder than is comfortable, this will help increase the stablization of the knee.

Laying on your back you can pull your knee to your chest, and then extend it, locking your knee holding the leg just over the ground..repeating, this will also help strengthen the muscles around the knee with minimal weight on it.

Always is good to speak with a doctor or physical therapist if you have concerns.
Output:
Does anybody know a good leg exercise? ( I have bad knees sooo...)?