To include a sub-level in a list on the next line underneath the main level of your list,

a
Press Tab
b
Press Shift+Tab
c
Use the Increase Indent button
d
Both A and C
e
None of the above

d. Both A and C

The correct answer is: d) Both A and C

To include a sub-level in a list on the next line underneath the main level of your list, you can:

a. Press Tab: This will indent the sub-level item and create a hierarchy in your list. When you press Tab, the item will appear indented from the main level item.

b. Press Shift+Tab: This will move the sub-level item back to the main level and remove the indentation. When you press Shift+Tab, the item will no longer be indented.

c. Use the Increase Indent button: Many text editors and word processors have an Increase Indent button in the toolbar. You can use this button to indent the sub-level item and create a hierarchy in your list.

d. Both A and C: Both pressing Tab and using the Increase Indent button will indent the sub-level item and create a hierarchical structure in your list.

e. None of the above: If you select this option, you are suggesting that there is another method to include a sub-level in a list, which is not listed above.

In this case, if you want to include a sub-level in a list on the next line underneath the main level, the correct answer would be d. Both A and C.