What is a document in MongoDB?

Select read concern levels that are supported by transactions in MongoDB.

Suppose you have a restaurants collection with the following document structure: { _id: ObjectId("5eb3d668b31de5d588f42931"), address: { building: '6409', coord: [ -74.00528899999999, 40.628886 ], street: '11 Avenue', zipcode: '11219' }, borough: 'Brooklyn', cuisine: 'American', grades: [ { date: ISODate("2014-07-18T00:00:00.000Z"), grade: 'A', score: 12 }, { date: ISODate("2013-07-30T00:00:00.000Z"), grade: 'A', score: 12 }, { date: ISODate("2013-02-13T00:00:00.000Z"), grade: 'A', score: 11 }, { date: ISODate("2012-08-16T00:00:00.000Z"), grade: 'A', score: 2 }, { date: ISODate("2011-08-17T00:00:00.000Z"), grade: 'A', score: 11 } ], name: 'Regina Caterers', restaurant_id: '40356649' } You don't have any indexes so far. What will the query plan look like for the following query?
db.restaurants.find( { "cuisine": "American" } )