[多选题]可作抛射剂使用的有（ ACD ）。
A.四氟乙烷
B.表面活性剂
C.丙烷
D.液化的二氧化碳

However important we may regard school life to be, there is no denying the fact that children spend more time at home than in the classroom. Therefore, the great influence of parents cannot be ignored or discounted by the teacher. They can become strong allies of the school personnel or they can consciously or unconsciously hinder and frustrate curricular objectives.
Administrators have been aware of the need to keep parents informed of the newer methods used in schools. Many principals have conducted workshops explaining such matters as the reading readiness program, manuscript writing and developmental mathematics.
Moreover, the classroom teacher, with the permission of the supervisors, can also play an important role in enlightening parents. The informal tea and the many interviews carried on during the year, as well as new ways of reporting pupils’ progress, can significantly aid in achieving a harmonious interplay between school and home.
To ill
A. participation in interesting activities relating to a subject improves one’s achievement in that area.
B. too many children are lazy and have poor work habits.
C. school principals do more than their share in interpreting the curriculum to the parents.
D. teachers should occasionally make home visits to parents.