get the first (or n'th) element in a jq json parsing

I can get the 1st element in a JSON inside []

$ echo \
    '[{"a":"x", "b":true}, {"a":"XML", "b":false}]' | \
    jq '.[1]'

{
  "a":
    "XML",
  "b":
    false
}

But if the json is already disassembled (for instance, after filtering entries using 'select'), how can I choose a single entry and avoid the error seen here?

$ echo \
    '[{"a":"x", "b":true}, {"a":"x", "b":false}, {"a":"XML", "b":false}]' | \
    jq \
      '.[] | select( .a == "x")'

{
  "a":
    "x",
  "b":
    true
}
{
  "a":
    "x",
  "b":
    false
}

$ echo \
    '[{"a":"x", "b":true}, {"a":"x", "b":false}, {"a":"XML", "b":false}]' | \
    jq \
      '.[] | select( .a == "x") | .[1]'

jq: error (at <stdin>:1): Cannot index object with number

You can wrap the results from select in an array:

jq '[.[]|select(.a=="x")][0]' your.json

Output:

{
  "a": "x",
  "b": false
}