The difference in water spray pattern between the high-velocity tip and low-velocity applicator used with the all-purpose nozzle is due to().
A. a difference in water pressure
B. the method of breaking up the water stream
C. the length of the applicator
D. All of the above
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蠕形螨是()
A. 无致病作用的寄生虫
B. 致病力较弱的寄生虫
C. 致病力较强的寄生虫
D. 机会致病寄生虫
E. 偶然寄生虫