Which of the following shows the most effective use of turn signals?

a. Some emirates have a corporate tax law, but it is applied only to foreign oil companies and foreign banks operating in those emirates.

b. Some emirates have a corporate tax law. Therefore, it is applied only to foreign oil companies and foreign banks operating in those emirates.

c. Some emirates have a corporate tax law. And it is applied only to foreign oil companies and foreign banks operating in those emirates.

d. Some emirates have a corporate tax law, so it is applied only to foreign oil companies and foreign banks operating in those emirates.