乙炔<在101325Pa即760mmHg下>密度为(),它的凝固点是(),汽化热为()。
参考答案:1.1747kg/m2;-85℃;799.16kj/kg
During the busiest season like National Day, Spring Festival, the traffic company provides
______ buses for the traveler. [ ]
A. extra
B. certain
C. various
D. unusual
淬火加热时防止氧化脱碳可采用哪些措施?