What is the difference between a mechanical wave and an electromagnetic wave?

A: A mechanical wave travels through empty space, while an electromagnetic wave travels through matter.
B: A mechanical wave has a short wavelength, while all electromagnetic waves have long wavelengths.
C: A mechanical wave has a high frequency, while all electromagnetic waves have low frequencies.
D: A mechanical wave travels through matter, while an electromagnetic wave travels through empty space.

The quote below is an excerpt from the charter of the united nations: "the purposes of the united nations are: to maintain international peace and security, and to that end: to take effective collective measures for the prevention and removal of threats to the peace, and for the suppression of acts of aggression or other breaches of the peace, and to bring about by peaceful means, and in conformity with the principles of justice and international law, adjustment or settlement of international disputes or situations which might lead to a breach of the peace . " source:this section implies that the united nations is prepared to do what to keep world peace?

Causes and effect chart for industrial revolution

Of the following, who would be the least affected by the telegraph? eastern industrialists western businessmen city dwellers native americans