The following table shows $\left(x, \; y\right)$ values for a linear function. What is the slope of this function?

A. $5$

B. $3$

C. $15$

D. $4$

E. $1$

$x$ | $y$ |

3 | 18 |

6 | 33 |

7 | 38 |

9 | 48 |

A. $5$

B. $3$

C. $15$

D. $4$

E. $1$