A Single Joint Expert Has Been Instructed by the Parties

A single joint expert has been instructed by the parties to an action. One of the parties is unhappy with the expert's conclusions. What can he do?
Which of the following options is the only option available to that party?

A) Nothing - he is stuck with the report.
B) Write to the expert and ask him to change his conclusion.
C) Ask your opponent if he will agree to the instruction of another single joint expert.
D) Apply to the court for permission to seek your own expert's report.