Does the MIT App Inventor have the ability to have a Radial Button selection?
Example?
The sample would be.
Select
- Celsius
- Fahrenheit
The coversion depends on which on the choose.
Like a Spinner?
If the selection is just between two options you can use the ready made "switch" user interface,like:

Alternatively you can use a Canvas in which to design a Sprite (with a dial button as a background image, for example). By rotating the Sprite a certain amount of degrees (Left or Right) you can implement a selector. Obviously the Switch block is much easier.
How about a pie chart, with selectable data points?
You're probably referring to the Radio Button. AppInventor doesn't have such a component, but you can use a similar one, CheckBox.

And then add some logic.
You can also create images representing radio buttons and set them as the background of a regular button. When clicked, the image changes to "selected."
You can use radio buttons in a Tableviewer, if you can use extensions:
Thank you all for your help. You gave me some things to try, and I will give each one a go.
Thank you again!