Sub-choices under the multiple choices

I have to create a question to ask respondents to select multiple choices. Within the multiple choices, I want to add sub-choices for two of the choices. For example,

• Select 1


• Select 2


• Sub-select 1


• Sub-select 2


• Sub-select 3


• Select 3


• Select 4


• Sub-select A


• Sub-select B


• Sub-select C