JSFiddle - React, Tailwind, and code Playground

HTML

<form>
    <div>
        <input type="radio" name="level0" value="A" id="A"/>
        <label for="A">A</label>
        <div class="sub1">
            <div>
                <input type="radio" name="level1" value="A0" id="A0"/>
                <label for="A0">A0</label>
            </div>
            <div>
                <input type="radio" name="level1" value="A1" id="A1"/>
                <label for="A1">A1</label>
            </div>
        </div>
    </div>
    <div>
        <input type="radio" name="level0" value="B" id="B"/>
        <label for="B">B</label>
        <div class="sub1">
            <div>
                <input type="radio" name="level1" value="B0" id="B0"/>
                <label for="B0">B0</label>
            </div>
            <div>
                <input type="radio" name="level1" value="B1" id="B1"/>
                <label for="B1">B1</label>
            </div>
        </div>
    </div>
    <div>
        <input type="radio" name="level0" value="C" id="C"/>
        <label for="C">C</label>
        <div class="sub1">
            <div>
                <input type="radio" name="level1" value="C0" id="C0"/>
                <label for="C0">C0</label>
            </div>
            <div>
                <input type="radio" name="level1" value="C1" id="C1"/>
                <label for="C1">C1</label>
            </div>
        </div>
    </div>
    <div>
        <input type="radio" name="level0" value="D" id="D"/>
        <label for="D">D</label>
        <div class="sub1">
            <div>
                <input type="radio" name="level1" value="D0" id="D0"/>
                <label for="D0">D0</label>
            </div>
            <div>
                <input type="radio" name="level1" value="D1" id="D1"/>
                <label for="D1">D1</label>
                <div class="sub2">
                    <div>
                        <input type="radio" name="level2" value="D10" id="D10"/>
                        <label for="D10">D1-0</label>
   ...

CSS

.sub1, .sub2 { display: none; }

:checked ~ .sub1, :checked ~ .sub2 {
    display: block;
    margin-left: 40px;
}