按照以下焊接操作步骤正确焊接顺序是： 1将烙铁头放在两个焊接面处加热。2待焊接面焊锡均匀熔化后，再顺管脚抽走烙铁头。3将焊锡丝顺烙铁头方向熔化到焊接面。4当焊锡熔化适量后，抽走焊锡丝。
A、1234‍
B、3412
C、1342
D、3241

单项选择题血红蛋白中的β珠蛋白位于（）号染色体上

单项选择题What is Salvation Army ? A. a Catholic charity and social services organization B. founded by William Booth and his wife Catherine Booth in London, in 1965 C. got the name because of a popular saying that “The Christian Mission is an army.” D. millions of Americans received help from it annually