41. Which command lists all indexes in a collection?

• a) db.collection.getIndexes()
• b) db.collection.listIndexes()
• c) db.collection.indexes()
• d) Both A and B

42. What is the purpose of the $merge stage in aggregation?

• a) Combines pipeline results with existing collection
• b) Merges multiple collections
• c) Deletes duplicate documents
• d) Splits large documents

43. Which operator checks array size in MongoDB?

• a) $size
• b) $length
• c) $count
• d) $arraySize

44. What does the $natural sort do?

• a) Returns documents in disk storage order
• b) Sorts alphabetically
• c) Orders by insertion time
• d) Randomizes document order

45. Which method is used for bulk write operations?

• a) bulkWrite()
• b) executeBatch()
• c) multiWrite()
• d) batchExecute()

46. What is the purpose of the $expr operator?

• a) Allows use of aggregation expressions in queries
• b) Executes JavaScript
• c) Validates query syntax
• d) Explains query execution

47. Which command repairs a MongoDB database?

• a) db.repairDatabase()
• b) db.fix()
• c) mongod --repair
• d) Both A and C

48. What does the $convert operator do?

• a) Changes a value's data type
• b) Converts collections
• c) Transforms queries
• d) Encodes BSON

49. Which operator performs a case-insensitive regex search?

• a) $regex with 'i' option
• b) $iregex
• c) $caseInsensitive
• d) $text with $caseSensitive:false

50. What is the purpose of the $facet stage?

• a) Executes multiple pipelines in a single stage
• b) Creates document facets
• c) Splits collections
• d) Optimizes queries

51. Which method returns distinct field values?

• a) distinct()
• b) unique()
• c) values()
• d) getDistinct()

52. What does the $geoNear operator do?

• a) Returns geospatial documents by proximity
• b) Creates geographic indexes
• c) Validates geoJSON data
• d) Measures distances

53. Which command flushes pending writes to disk?

• a) db.fsyncLock()
• b) db.flush()
• c) db.sync()
• d) db.commit()

54. What is the purpose of the $dateToString operator?

• a) Formats date as string
• b) Converts string to date
• c) Validates dates
• d) Extracts date parts

55. Which operator checks if a field is an array?

• a) $isArray
• b) $type
• c) $arrayCheck
• d) No direct operator (use $type with "array")

56. What does the $binarySize operator return?

• a) Size of a binary field in bytes
• b) Binary data hash
• c) Binary encoding type
• d) Binary checksum

57. Which method creates a capped collection?

• a) db.createCollection("name", { capped: true, size: 100000 })
• b) db.addCappedCollection()
• c) db.collection.cap()
• d) db.makeCapped()

58. What is the purpose of the $indexOfBytes operator?

• a) Returns byte position of substring
• b) Creates byte indexes
• c) Counts bytes
• d) Validates UTF-8

59. Which command lists all running operations?

• a) db.currentOp()
• b) db.operations()
• c) show processes
• d) db.processes()

60. What does the $toUpper operator do?

• a) Converts string to uppercase
• b) Capitalizes words
• c) Converts to title case
• d) Escapes uppercase chars