Copper and tin are constituent of
bronze
B
Since German silver is an alloy formed from the homogenous mixing of Copper (Cu), Zinc (Zn), and Nickel (Ni), this option is incorrect.
C
Since Brass is an alloy formed from the homogenous mixing of Copper (Cu) and Zinc (Zn), this option is incorrect.
Hence, option A is correct. Copper and tin are found in Bronze.