Which statement is true of magnets? A. A magnet always has two poles.
B. Earth is a permanent magnet. C. Electromagnets always have the same strength.
D. Electromagnets are generally weaker than permanent magnets.

Option A

Explanation:

A magnet has always two poles.

1) North Pole

2) South Pole

However,

=> Earth is a temporary magnet.

=> Electromagnets don't have the same strength.

=> Permanent magnets are weaker than electromagnets.

the transfer of energy between two molecules spaced just nanometers apart plays a key role in many technologies, including photovoltaics, quantum information systems, lighting, and sensors, as well as in biophysics to measure nanometer distances and in photosynthesis. but an open question in this area is what effect, if any, the surrounding photonic environment has on this nanoscale energy transfer. by designing and performing a carefully controlled experiment to answer this question, scientists have settled the debate and found clues to improving the efficiency of many of the technologies that rely on this process.

explanation: