Match List-I with List-II:
| List-I (Modulation Schemes) | List-II (Wave Expressions) |
|---|---|
| (A) Amplitude Modulation | (I) \( x(t) = A\cos(\omega_c t + k m(t)) \) |
| (B) Phase Modulation | (II) \( x(t) = A\cos(\omega_c t + k \int m(t)dt) \) |
| (C) Frequency Modulation | (III) \( x(t) = A + m(t)\cos(\omega_c t) \) |
| (D) DSB-SC Modulation | (IV) \( x(t) = m(t)\cos(\omega_c t) \) |
Choose the correct answer:

A block of certain mass is placed on a rough floor. The coefficients of static and kinetic friction between the block and the floor are 0.4 and 0.25 respectively. A constant horizontal force \( F = 20 \, \text{N} \) acts on it so that the velocity of the block varies with time according to the following graph. The mass of the block is nearly (Take \( g = 10 \, \text{m/s}^2 \)): 
A system that describes the information exchange between two points is called the communication system. The transmission and reception process of information is called communication. The major elements of communication are such as:
The following are the examples of communication systems:
Turning on Signal specification or technology, the communication system is categorized as follows:
