There are some lenses available in the laboratory as follows, to make the observed object magnified 50 times, the lenses to be chosen are ( ) A. ① and ③ B.

Test analysis: the objective lens has a spiral, the eyepiece does not have a spiral, so as to identify the lenses of the microscope, the ① ② ⑤ in the figure is the objective lens, ③ ④ ⑥ is the eyepiece. The longer the eyepiece, the smaller the magnification, the shorter the objective lens, the smaller the magnification. The magnification of the microscope is equal to the product of the magnification of the eyepiece and the magnification of the objective lens.