Use the ledge to the right of the morph tunnel to safely wait for the acid to go down.

Requires:

"Morph"
"canDash"
{
  "heatFrames": 660
}
{
  "or": [
    "canDodgeWhileShooting",
    {
      "acidFrames": 20
    }
  ]
}

Clears obstacles: B