解答:解:如图:∵∠A=∠P1P2A=15°∴∠P2P1P3=30°,∠P1P3P2=30°∴∠P1P2P3=120°∴∠P3P2P4=45°∴∠P3P4P2=45°∴∠P2P3P4=90°∴∠P4P3P5=60°∴∠P3P5P4=60°∴∠P3P4P5=60°∴∠P5P4P6=75°∴∠P4P6P5=75°∴∠P4P5P6=30°∴∠P6P5P7=90°,此时就不能在往上焊接了,综上所述总共可焊上5条.故应选B.