Answer: B) 19 Explanation: Second, fourth and the sixth digits of the number are 3, 1 and 6. Using these digits only once we can make 361, which is a perfect square number. Hence, our answer is 19 x 19 = 361

Answer: A) Succession Explanation: The process which wherein an Ecosystem may renew itself is known as Ecological Succession. The time scale may be decades or a million of years after a mass extinction.  It may be achieve over a period of time.

Answer: A) 2Mg + O2 ----> 2MgO Explanation: 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.