661: The persons start walking at a steady pace of 3 km/hour from a road 1 intersection along two roads that make an angle of 60° with each other. What will be the (shortest) distance separating them at the end of 20 minutes ?
(a) 3 km
(b) 2 km
(c) 1.5 km
(d) 1 km
662: Zero was invented by
(a) Aryabhata
(b) Varahamihira
(c) Bhaskara I
(d) an unknown Indian
663: Which of the following two continents are just like the mirror images of each other?
(a) South America and Africa
(b) South America and North America
(c) South America and Australia
(d) Europe and Asia
664: The annual range of temperature in the interior of the continents is high as compared to coastal areas. What is / are the reason / reasons?
1. Thermal difference between land and water
2. Variation in altitude between continents and oceans
3. Presence of strong winds in the interior
4. Heavy rains in the interior as compared to coasts
Select the correct answer using the codes given below.
(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 2 and 3 only
665: There is some concern regarding the nanoparticles of some chemical elements that are used by the industry in the manufacture of various products. Why?
1. They can accumulate in the environment, and contaminate water and soil.
2. They can enter the food chains.
3. They can trigger the production of free radicals.
Select the correct answer using the code given below.
(a) 1 and 2 only
(b) 3 only
(c) 1 and 3 only
(d) 1, 2 and 3