________ you have to do the job, you should try your best to do it well even though it may be very difficult for you.

A．Since

B．While

C．Unless

D．Though

消防头盔的冲击力指标：5kg钢锤自1m高度自由下落冲击头盔，头模所受冲击力的最大值不超过4580N。