Registering to watch a webinar via the Zoom API, can't register multiple value for custom question

Hi, I am not an English speaker so I may be rude.

I am using the following endpoints of the ZoomAPI to register for viewing.

POST /webinars/{webinarId}/registrants

We also register required multiple custom questions in the following format (json)

"custom_questions":[
            {
                "title":"short_column",
                "value":"test"
            },
            {
                "title":"single_radio_column",
                "value":"B"
            },
            {
                "title":"single_dropdown_column",
                "value":"b"
            },
            {
                "title":"multiple_ column",
                "answers":["a","b","c"]
            },
            ]
        }

But only the value of multiple does not seem to register properly.
The following is a confirmation of the registration details using GET webinars/{webinarId}/registrants.

            "custom_questions": [
                {
                    "title": "short_column",
                    "value": "test"
                },
                {
                    "title": "single_radio_ column",
                    "value": "B"
                },
                {
                    "title": "single_dropdown_column",
                    "value": "b"
                },
                {
                    "title": "multiple_ column"
                }
            ],

Is this a bug in Zoom’s internal processing, since I don’t get any errors when using the registrants API and the value is definitely included when the request is sent?

Please let me know if my request is incorrect!

Anyone else in the same situation as me?