Step 1: Karbate Identification.
Karbate is defined as an alloy composed of copper and nickel, recognized for its widespread use in industrial settings owing to its inherent resistance to corrosion and its robust nature.
Step 2: Options Analysis.
- (A) Karbate is accurately described as an alloy of copper and nickel.
- (B) Chemically impregnated carbon is not synonymous with Karbate.
- (C) High silicon iron is unrelated to Karbate.
- (D) Karbate is not an alloy comprising copper, tin, and zinc.
Final Answer: \[ \boxed{\text{A) an alloy of copper and nickel}} \]