Identify a line with an undefined slope .Application
a. y = x
b. y+ x =0
c. y = 10
d. x = 1

The correct answer is: ∴ Option d i.e. x = 1 is the correct option.

Step-by-step solution:-
We know that when a line, plotted on a graph is represented by a verticle line, its slope is undefined.
i.e. slopes of lines that are parallel to y-axis are undefined.
Equations of lines that are parallel to y-axis are in the form x = a where a is the value of x-intercept.
From the given options, option d is the only option with equation of line in this format i.e. x = a i.e. x = 1.
∴ option d is the correct option.