Questions

B is correct, an abstract class need not implement any or all of an interface’s methods

Given Equation is 

Mg + O2 → MgO

Balancing the Chemical Equation is nothing but Conservation of Matter. As Matter is Neither created nor Destroyed, it must be conserved.

Here we have 1 Mg and 2 O on the left side and 1 Mg and 1 O on the right side

To balance that, add 1 Mg on the left side so that it becomes 2 Mg and 2 O on the left side

i.e,

2 Mg + O2 → 2 MgO

Here it has 2 Mg & 2 O on the left side and 2 Mg and 2 O on the right side and the Chemical equation is Balanced.

Microsoft Office is an example of a Horizontal market software.

In computers, software is a collection of programs which performs a task. Horizontal market software is an application software that is useful in a wide range of industries. Horizontal market software is also known as "productivity software."

Examples :

Email, Payroll, Operating Systems (OS), Spread sheets, etc...

'Rhythm of eyes' logically means Nainital in India.

The other cities are:

No Zip - Chennai

Mr. City - Srinagar

Do Acting - Karnataka.

Golf player Vijay Singh is an Indo-Fijian belongs to Fiji. He was born in 1963, who was number 1 in the Official World Golf Ranking for 32 weeks in 2004 and 2005.

He was nicknamed as "The Big Fijian", has won three major Golf Championships. He has started his profession career from 1984.

The Central Excise Day (CED) is celebrated every year on February 23 in India to commemorate the enactment of the Central Excise and Salt Act, 1944. The Central Excise officers all over the country celebrate this day by organizing seminars, workshops, trade interactions and cultural events etc.

Everyone has special skills; some people use them very well is the sentence which is correctly punctuated.