Transfer function and its zeros:
A transfer function is a mathematical representation of the relationship between the input and output of a system. It is commonly used in control systems analysis and design. The transfer function is usually represented in the form of a ratio of polynomials, where the numerator represents the output and the denominator represents the input.

The zeros of a transfer function are the values of s (complex variable) for which the numerator of the transfer function becomes zero. In other words, they are the values of s that make the output zero.

Zero at infinity:
A zero at infinity is a special type of zero in the transfer function. It means that the numerator of the transfer function becomes zero as s approaches infinity. In other words, the output becomes zero for very large values of the complex variable s.

Relation between numerator and denominator degree:
The degree of a polynomial is the highest power of the variable in the polynomial. In the context of transfer functions, the degree of the numerator is the highest power of s in the numerator polynomial, and the degree of the denominator is the highest power of s in the denominator polynomial.

Explanation of the answer:
In this question, it is given that the transfer function has two zeros at infinity. This means that the numerator of the transfer function has two factors of (s^n), where n is a positive integer, that cancel out with the denominator factors of (s^m), where m is a positive integer.

Since the zeros at infinity cancel out with the corresponding poles at infinity, the degree of the numerator is reduced by 2 compared to the degree of the denominator. Mathematically, we can express this relationship as:

N = M - 2

where N is the degree of the numerator and M is the degree of the denominator.

Hence, the correct answer is option B: N = M - 2.