In MongoDB, if we have subdocuments we can ___ Select one: a. use the subdocuments to store data without limits. b. express queries using the fields of subdocuments. c. All the choices d. not nest another subdocument inside a subdocument. code example

System.findOne({ 'nodes.main.Alpha': 23000}, function(err, system){
   if(err){console.log(err);}
   else{console.log(system);}
 });