Which is an equation of a line with undefined slope?

Any constant that is set to equal x would have an undefined slope.  For example, x=0 is just a horizontal line, so the slope is undefined.  

Step-by-step explanation:

The slope would be undefined because in a horizontal line, the length could be anything, but there is no distance between x-values.

it depends on the weather. because i have flown to seattle when it was pouring down rain and there was one time i flew to ohio when it was snowing hard. whats your situation.

step-by-step explanation:

konichiwa~! my name is zalgo and i am here to answer your anime-related question today. more than likely, kirishima would kill izuku, marry mino and kiss momo. all of this would be my opinion by the way. (and i am also a weeb lol)

i hope this you! : d

stay and stay proud! " - zalgo

(and do you think you can mark me as brainliest? i'd greatly appreciate it! arigato~! )