Answer:
he horizontal line test is used to determine if a function is one-to-one. 
It works by testing if a horizontal line intersects the graph of a function once or more than once. 
If the horizontal line intersects the function's graph more than one time, that means the function is not one-to-one. 
This means answer choice A is true. 
 
In a function, every input must be paired with exactly one output. 
If a single number appears more than once, both as input values, the relation is not a function. 
This means answer choice B is incorrect. 
 
The vertical line test is used to determine whether or not a curve in a graph represents a function or not. 
This works by checking if any inputs, x-values, are paired with multiple outputs, y-values, by drawing a vertical line through points on the curve. 
This means answer choice C is true. 
 
A sequence is a data set, or just set of numbers, that follow a specific pattern. 
This could be by a common difference or common ratio. 
Sometimes sequences are defined as functions with a domain of natural numbers. 
Natural numbers are whole positive numbers. 
Rational numbers are are numbers that can be written as a simple fraction. 
Rational numbers can be decimals, fractions, and even negative. 
While answer choice D is close to being true, the domain of sequences is always natural, numbers, not rational. 
This means answer choice D is incorrect. 
 
Answers: 
A. The horizontal line test may be used to determine whether a function is one-to-one 
C. The vertical line test may be used to determine whether a relation is a function. 
Explanation: