Questions

The given sentence is grammatically correct and there is no error.

This can be interpreted from these lines of the passage, “Sanctions also play a dramatic role as an offensive militaristic manoeuver” and "Indeed, economics is often used directly as a weapon of war and conflict via trade sanctions."

Sunspots are a magnetic phenomenon on the Sun.

The reason a sunspot appears dark is that they are cooler than the rest of the Sun's surface and also the gas inside the spot where the magnetic field is strongest is only emitting about 1/4 as much light as from the rest of the solar surface. 

The reason for transmitting data over optical fibers, is because the speed of data transmission through optical wires are equal to the speed of light. The intense speed of data transfer speed, has lead to the use of optical fibers. The optical fiber uses the technology of transferring light beams, from one end to the other end of optical cables. The attenuation in optical fiber is due to Scattering. The reason why scattering is caused, due to the folding, in the wire.