Vapours of acetic acid smell

To find the focal length of a concave mirror, Sita should choose which one of the following set-ups?

Iron nails were dipped in an aqueous solution of copper soleplate. After about 30 minutes, it was observed that the color of the solution changed from

A student added acetic acid to test tubes I, II, III and IV containing the labeled substances and then brought a burning splinter near the mouth of each test tube.

The splinter would be extinguished when brought near the mouth of test tube.

The steps involved in observing a slide under a microscope are given below. They are not in proper sequence.

I. Focus the object under high power microscope.

II. Place the slide on the stage of the microscope.

III. Arrange the mirror to reflect maximum light to the slide.

IV. Focus the object under low power of microscope.

The proper sequence of steps is