The correct answer is A) gear driven by the engine. In a two-stroke cycle diesel engine, the Roots-type blower is typically gear driven by the engine. This arrangement allows the blower to provide the necessary scavenging air for the engine, ensuring efficient combustion and removal of exhaust gases. The blower is mechanically coupled to the engine crankshaft, allowing it to operate in sync with the engine's rotation. The other options are incorrect because: B) driven by an exhaust gas turbine is not common in a two-stroke diesel engine, C) actuated by the intake valves would not provide the necessary air flow, and D) driven by a separate motor would require additional power and complexity that is not typically found in this type of engine configuration.