Questions

The physical components of a computer are referred to as Hardware of the computer. 

The hardware components of the computer includes :

• Processor.
• Main memory.
• Secondary memory.
• Input devices.
• Output devices.

The USSR( now a Common Wealth of Independent States) is spread over Europe and Asia

Africa - 54 countries

South America - 12 countries

Antarctica - 0 countries

Europe - 43 countries.

Hence, Antarctica continent has the least countries.

When the resistance of the air between breaks down the current flows from the positive cloud to the negative cloud in a flash which we call lightning . The difference of potential involves is very high.

In chemistry, the term transition metal has three possible meanings: The IUPAC definition defines a transition metal as "an element whose atom has a partially filled d sub-shell, or which can give rise to cations with an incomplete d sub-shell".

Any of the set of metallic elements occupying a central block (Groups IVB–VIII, IB, and IIB, or 4–12) in the periodic table, e.g. iron, manganese, chromium, and copper. Chemically they show variable valency and a strong tendency to form coordination compounds, and many of their compounds are coloured.

Here in the given options, only iron (Fe) is a transition metal since Strontium is an alkaline earth, arsenic is a metalloid, hydrogen is (normally) a diatomic gas.