Answer: B) 45 yrs Explanation: Let father's age be x year and son's age be y year. According to question, 2(x+y) = 8y _______(I) and (x+y)/2 = 30 => x+y = 60 years__________(II) From equation (I) and (II) 8 y = 120 y = 15 years, Hence x = 45 years.

Answer: B) They contain free electrons Explanation: Metal particles are held together by strong metallic bonds, which is why they have high melting and boiling points. The free electrons in metals can move through the metal, allowing metals to conduct electricity. Because the electrons in the atom's higher energy levels can separate from the atoms easily, they can be pulled out with very little energy. Because the molecular structure of the metal is such that 'free electrons' are free to move, thus being categorized as electrically conductive.   For example, copper is used for electrical wiring because it is a good conductor of electricity.

Answer: B) 40 sec Explanation: Speed of train relative to jogger = 45 - 9 = 36 km/hr.= 36 x 5/18 = 10 m/sec. Distance to be covered = 260 + 140 = 400 m. Time taken = 400/10 = 40 sec.

A child selector is used when you want to match an element that is the child of another specific element.The parent and child selectors are separated by spaces.The following selector locates an unordered list element within a paragraph element and makes a text within that element bold. p > ul {font-weight: bold;}