active-section-name
<template>
<lightning-card>
<lightning-accordion active-section-name="B">
<lightning-accordion-section name="A" label="Accordion Title A"
>This is the content area for section A</lightning-accordion-section
>
<lightning-accordion-section name="B" label="Accordion Title B"
>This is the content area for section B</lightning-accordion-section
>
<lightning-accordion-section name="C" label="Accordion Title C"
>This is the content area for section C</lightning-accordion-section
>
</lightning-accordion>
</lightning-card>
</template>
