Both b and c are correct because since OBD II (On-Board Diagnostic Level II), the industry has used a 5 character diagnostic trouble code that can only be read with another computer like a scan tool or PC based laptop computer.

Coolant is orange, pink or green. Engine oil is yellow or brown. ATF is red. Washer fluid is blue.

Tech A is right because you need to apply a light coat of engine oil to new oil seals to help ease them in. Tech B is wrong because installing the intake oil seal into the exhaust side or installing the exhaust oil seal into the intake side can cause problems later because the exhaust side is generally hotter than the intake side and the seals are generally different and made of different material and therefore not interchangeable.

Valve adjustment is necessary following the replacement of any valve train or cylinder head.

Spraying the block with a rust inhibiter and wrapping the engine with a plastic bag keeps the engine free from corrosion until you are ready to assemble it.. The other chemicals are not as effective.

The top of the cylinder is where the maximum temperature is found.

Tech A is right because a weak solution of antifreeze may cause corrosion build-up in the cooling system. Tech B is wrong because most original equipment manufacturers (OEM) recommend that the coolant be changed at specified intervals due to a loss in corrosion inhibitor life.

The oil pump will slow down not speed up when an oil filter becomes clogged. A, b and c will occur when an oil filter becomes clogged.

This is the MOST likely cause of the 4 choices. The CDR (crankcase depression regulator) is designed to depress or reduce the crankcase pressure. If it is stuck closed, the pressure in the crankcase increases and pushes the oil out.

Ash is mostly material left over after oil is burned in the combustion chamber. Ash must be physically removed from a DPF since it cannot be regenerated. The other choices do not apply to a DPF.

A short or long replacement line that is different than the original will change the timing in the number 3 cylinder and cause a rough idle or misfire. B is wrong because a glow plug failure does not cause a misfire or rough idle on an engine when hot. C is wrong because a glow plug failure does not cause a misfire or rough idle on an engine when hot. D is wrong because high Cetane fuel does not cause a misfire. High Cetane numbers indicate good ignition quality resulting in a short delay period and low Cetane numbers indicate poor ignition quality that results in a long delay period. Low Cetane numbers can cause a long ignition delay, which can cause a hard starting with white smoke and misfiring cylinders.

The intake pipe of the high pressure pump is where the pump will have lowest pressure. A is wrong because positive pressure would be present at the outlet pipe. B is wrong because positive pressure would be present at the inlet of the secondary air filter. D is wrong because positive pressure would be present at the inlet side of the primary filter.