练习材料：
Lesson20-3 Snake poison
Vipers (adders) and rattlesnakes manufacture the blood poison, which is known as haemolytic. Both poisons are unpleasant, but by far the more unpleasant is the blood poison. It is said that the nerve poison is the more primitive of the two, that the blood poison is, so to speak, a newer product from an improved formula. Be that as it may, the nerve poison does its business with man far more quickly than the blood poison. This, however, means nothing. Snakes did not acquire their poison for use against man but for use against prey such as rats and mice, and the effects on these of viperine poison is almost immediate.
应用配置：L0+L4
知识笔记： rattlesnakes/ haemolytic/
练习感悟：用时32分。声音有点不适，段落较短，还是比骄容易。
