Monomial algebraic expression is - \( \begin{array}{ll}\text { (a) } 4 x & \text { (b) } 4 x+3 y \\ \text { (c) } 3 x+2 y & \text { (d) } 3 x+2 y+5 z\end{array} \)

A monomial algebraic expression consists of a single term that includes a coefficient and variable(s), without any addition or subtraction of separate terms. So, from the options provided, \(4x\) is the only monomial since it represents a single term. Monomials can be expanded into more complex polynomials by introducing more variables and coefficients, which leads to fascinating mathematical concepts. For instance, if you take the monomial \(4x\) and multiply it with \(3y\), you get a product of \(12xy\), expanding your algebraic expression into a binomial! This transformation is the basis for polynomial equations, opening doors to complex problem-solving in algebra.