乐音体系中的音级b1、a2、G在五线谱上的准确位置是( )<br>· <img src="/lqwvjeImg/dc/dcaab198178e533eb5a0e3e37ebd95dc.png"style="width:123px;height:49px;"><br>· <img src="/lqwvjeImg/40/40e75073d376f2085ce97b02aa75fcd2.png"style="width:138px;height:51px;"><br>· <img src="/lqwvjeImg/ce/ce2260858827c9f9bc01fe6e6e8d4422.png"style="width:133px;height:49px;"><br>· <img src="/lqwvjeImg/b0/b0fcbd2480a77247ed10de806692f110.png"style="width:131px;height:46px;">