Which procedure must be completed before switching to high power objective on a microscope

1.turn  the  revolving  turret  so  that low  power  lens  come  into  position
2 place  the  microscope  slide  on  the  stage
3 look  at  the  objective  lens  and the  stage  from  the   side  as  you  turn   adjust  knob  so  that  stage   can  move  upward
4 look  through  the  eyepiece  and  move  the    focus  knob  until  image  come  into  focus
5.adjust  the   condenser   to regulate  thee  amount of  light
6 move  the  microscope  slide  around  until  the  sample  is  in  the   center of  field  of  view

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.

Precipitate, and gas