Signal sighting does not prevent but reduce the risk of... sighting also ensures compliance to all relevant standards. Often, the term hazard and risk are mixed.
b) seems a disproportionate length to c) although both at worth 10 marks. Time is king.
Signal visibility is especially important and line speeds increase and OLE creates lots of obstructions that can cause read across issues as the relevant aspect disappears. NR has standards that define minimum reading time and how/when obstructions are permitted.