Please Explain why answer was chosen

QUESTION 13: What makes a fiber optic (FO) cable work?

		a. total internal reflection (TIR) is achieved provided the core and cladding have the same refractive indices
		b. FO light propagation only occurs when there is line-of-sight (LOS) between the source and detector
		c. light propagation occurs when the refractive index of the core differs from the refractive index of the cladding
		d. none of the above

QUESTION 14:Select the correct statement(s) regarding SMF and MMF fiber optic cables.

		a. since MMF cables support multiple modes of light, it has greater capacity and supports greater distances compared to SMF
		b. Both MMF and SMF can be designed with step index or graded cores
		c. SMF propagates a single mode of light, thus reducing signal distortion
		d. all of the statements are correct

QUESTION 15:With amplifiers, both the desired signal and unwanted noise are amplified. This differs from the repeater, which repeats the digital signal without the noise.

True False

QUESTION 16:Identify the correct group of propagation modes and impediments which impact unguided signal transmissions.

		a. reflection, scattering, diffraction
		b. refraction, modal dispersion, direct LOS
		c. reflection, absorption, impedance
		d. crosstalk, modal dispersion, absorption