The correct answer is (a) Mil Std 1553
The best I can explain: Mil Std 1553 is a US military standard data bus which came out in the 1970s in the F-16 and the following models of fighter aircraft. It has a data rate of 1Mbit/sec and a word length of 20 bits to encode clock, data, and address and so can receive or transmit up to 50,000 data words a second.