[{title:"test1",imgUrl:"test2",SKU:"test",topics:[{topicTitle:"1",questions:[{section:"A",setup:"",question:"",correct:"",answer:"",note:"",questionNumber:"",a:"",b:"",c:"2",d:"Old_value",e:""},],},],}]

db.collection.update({},{$set:{"topics.$[x].questions.$[y].d":"New_Value"}},{arrayFilters:[{"x.questions":{$exists:true}},{"y.c":"2"}]})