Which of the following function is for single checkbox widget?

The correct answer is A. checkboxInput.

A checkboxInput is a widget that allows users to select one or more options from a list. It is typically used to allow users to indicate their preferences or to provide feedback.

A dateInput is a widget that allows users to enter a date. It is typically used to allow users to specify a date for an event or to filter data by date.

A singleboxInput is a widget that allows users to enter a single line of text. It is typically used to allow users to enter their name, email address, or other contact information.

All of the mentioned are not correct because only checkboxInput is a function for single checkbox widget.