In the following questions, a sentence/a part of the sentence is written in bold. Below are given alternatives to the bold part which may improve the sentence. Choose the correct alternative. In case no improvement is needed, choose No Improvement.
Thomas Caffall the gunman killing two persons near the Texas A & M University, asked forgiveness for shooting the officers

Options

A. No improvement
B. who has killed
C. who has killed
D. who had killed

Answer

B