[Q]: Which of the following solutions is better for the following goal:
How to prevent your garden producing stubby carrots?

[A]: The carrots are root vegetables, meaning you are eating the roots. If you provide the carrots with enough room they will grow as long as a foot or more. You can do this by making a raised bed, with loose enough soil so the carrots are able to develop sufficiently downward.

[Q]: Which of the following solutions is better for the following goal:
air humidifier

[A]: take ice block and place in front of fan

[Q]: Which of the following solutions is better for the following goal:
To pass a drug test after having smoked pot.

[A]: Pay someone in your city who doesn't do drugs to give you some clean urine to use.

[Q]: Which of the following solutions is better for the following goal:
How can I easily thread a needle?

[A]:
Make sure the end of the thread has a sharp point, and that you use a needle with a wide eye that can accommodate the thread. Insert the thread into the eye of the needle, use a needle threader of necessary.