Changing a dropdown list's content with a variable.

Changing a dropdown list's content with a variable.

Thanks in advance for any help!
Here is what I'm working with:

Form A (created from a spreadsheet):
Has 3 columns labelled: Fruit, Vegetable, Grain
Each column has several related entries.

Form B
Contains:
Dropdown List 1:  Which displays the choices Fruit, Vegetables, Grain.
Dropdown List 2:  I would like this dropdown list to display choices from the appropriate column in Form A, depending on which which choice was selected in Dropdown List 1.

I'm new to Zoho Creator so I know there's a way of doing this, I just haven't been fully grasping the tutorials I've been looking at so far.

Cheers,
Mike