Researchers have announced that the magnetic fields emitted by one manufacturer’s security surveillance system, of which type there are 200,000 worldwide, can interfere with pacemakers and that this interaction can bring on missed or irregular heartbeats, nausea, breathlessness, dizziness, and even fainting.
- of which type there are 200,000 worldwide, can interfere with pacemakers and that
- of which, worldwide, there are 200,000 of that type, and which can interfere with pacemakers, and
- of which type there are 200,000 worldwide, they can interfere with pacemakers and
- 200,000 of which type exist worldwide, interfering with pacemakers, and
- 200,000 of that type existing worldwide and can interfere with pacemakers, and
Answer is D, I dont understand. Mine is A. | 
