Humans sleep in cycles, usually two or three cycles per night. there is a point in each cycle when waking up will leave the sleeper feeling the most rested and refreshed. after learning about this, a computer programmer designed a new smartphone alarm clock. this new alarm clock uses sensors in the smartphone to detect the sleeper’s motion and determine when the sleeper has reached the best point in the sleep cycle at which to wake up. the app can be downloaded onto any smartphone. most users who download this app find that it does not them wake up feeling more refreshed, but they are willing to try improved products in the future. which criterion did this sleep cycle alarm clock fail to meet? it did not solve the problem. it was not cost effective enough. it was not readily available. it was not safe for most users.

it did not solve the problem

It did not solve the problem.

Explanation: Basically, if people download a sleep cycle alarm clock app to wake up feeling more refreshed but it does not happen, the problem is not solved.

For the rest of the options we need to know more information that is not available in the text. For example, the cost of the app.

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the aurora is formed when charged particles emitted from the sun during a solar flare penetrate the earth's magnetic shield and collide with atoms and molecules in our atmosphere. these collisions result in countless little bursts of light, called photons, which make up the aurora.

auroras are generated by charged solar particles hitting molecules in earth's atmosphere. this usually happens in high latitudes, because our planet’s magnetic field tends to funnel these particles toward the poles. that’s why it can be experienced in northern ohio.