Which function's graph is the widest parabola?

You can look at this graph:     https://www.desmos.com/calculator/8albvsjxnd

And move the slider under  a  to see what happens as  a  gets smaller and bigger.

You should be able to see that as the value of  a  gets smaller, the parabola gets wider.

So you're right, the widest parabola is  c.  y = (1/8)x²   

Don't you wish that ice cream worked that way  ??

Eat  (1/3) of a bowl....you get  "wider'

Eat 3 bowls.....you get  "narrower "