单项选择题 射吸式普通割嘴的割嘴头部与割炬连接座的配合角锥度为（ ）度。

未知题型 2. Take a closer look at the following sentences, and correct any mistakes involved. (1) Modern irrigation techniques are more efficiency than traditional ones. (2) Poor diet can lead to a number of healthy problems. (3) After 3 weeks the average high of the plants increased by 12.6 centimetres. (4) Sells of ice-cream usually increase significantly in the summer. (5) The danger of driving too fastly in urban areas was highlighted in the report.

单项选择题 集中精力做某件事，一段时间就能达到好的效果，心里学家把它叫（）法则