Refer to figure. 
Learning Objective 010.06.07.01.06: State the radar requirements for simultaneous, independent, and parallel instrument approaches, and how weather conditions effect these. Source: ICAO Doc 8168, Volume III, Section 3, Chapter 1; ICAO Doc 4444, Chapter 6

For independent parallel instrument approaches, aircraft on adjacent final approach courses are separated without relying on longitudinal spacing between the aircraft. Because of this, continuous radar monitorin is required to ensure that an aircraft does not inadvertently deviate toward the adjacent approach path and enter the No Transgression Zone (NTZ).

As for the options:

Supported by radar vectoring. ---> INCORRECT. Radar vectoring is commonly used to establish aircraft on the final approach course, but it is not a mandatory requirement for independent parallel approaches. Aircraft may also join the final approach via approved procedural methods, provided the procedure satisfies the requirements for independent parallel operations.

Conducted as visual approaches. ---> INCORRECT. Independent parallel approaches are instrument approach procedures. In fact, the concept was developed specifically to allow simultaneous instrument operations, often in reduced visibility conditions. They are therefore not required to be visual approaches.

Monitored by radar.---> CORRECT. Continuous radar monitoring is a fundamental requirement for independent parallel approaches. Controllers must be able to detect any aircraft deviating toward the NTZ and immediately issue corrective instructions to maintain safety between the parallel approach streams.

Are only conducted by turbojet aeroplanes. ---> INCORRECT. There is no requirement restricting independent parallel approaches to turbojet aircraft. Eligibility depends on the aerodrome, the approach procedure, surveillance capability, and aircraft operational approval, not on engine type.

Remember:

Dependent parallel approaches = spacing between aircraft is part of the solution.
Independent parallel approaches = radar monitoring is part of the solution.