An airplane has retractable landing gear. What additional instrument is required for VFR flight during the day?

1. 1A landing gear position indicator
2. 2A gear warning horn at the throttle
3. 3An emergency gear extension handle
4. 4A second airspeed indicator

Source: 14 CFR Part 91, § 91.205 Powered civil aircraft with standard U.S. airworthiness certificates: Instrument and equipment requirements.