Answer: A) Air pollution Explanation: 1. Lichens are plants that grow in exposed places such as rocks or tree bark.   2.  Lichens are widely used as environmental indicators or bio-indicators. They can be used as air pollution indicators, especially of the concentration of sulfur-di-oxide in the atmosphere.     3. They need to be very good at absorbing water and nutrients to grow there.

Answer: C) The number of protons is equal to the number of electrons. Explanation: The number of protons is equal to the number of electrons. That is the number of positive charges is equal to the number of negative charges.

Answer: B) Token Ring Explanation:

Answer: D) 320 m Explanation: Relative speed = (72 - 36) x 5/18 = 2 x 5 = 10 mps.Distance covered in 32 sec = 32 x 10 = 320 m. The length of the faster train = 320 m.

Answer: A) Fourth generation Explanation: Microprocessors are used in the computers of fourth generation computers. Personal microcomputers were possible due to the microprocessors.   Microprocessors further revolutionized the development of computers.   The first microprocessor called Intel 4004 was developed by American Intel Corporation in 1971.

Answer: C) Tailor Explanation: Here Pen is a tool which is used to write and poet uses it. Then, the needle is a tool which is used to stitch and it is used by Tailor. Except tailor, none of the other options is a person to use it.   Hence, Pen : Poet :: Needle : Tailor

Answer: A) 5 km Explanation: