For example, did you know that 1 in 4 teenagers has tried marijuana?
比如,你是否知道4个青少年中就有1位曾经吸过大麻?
The operation, which lasted for over four hours, proved to be very difficult because of the hard resin which covered the skin.
手术持续了4个多小时,非常难做,因为皮肤上覆盖着一层硬硬的树脂。