Answer: B.) He is concerned about the course of his experiment.
Dr. Jekyll is a meticulous, dedicated and friendly doctor, who nevertheless, sometimes is consumed with evil thoughts. In order to rid himself of these, he develops a serum. This experiment causes the evil thoughts to be personified in the character of Mr. Hyde.
In this passage, we can see that the doctor has performed his experiment, and is reflecting on the "issues and possibilities" of the outcome. This shows that he had become concerned about the course of his experiment.