Answer: A) 5 kmph Explanation: Speed of the boat downstream  s=a/t= 60/3 = 20 kmph Speed of the boat upstream s= d/t = 30/3= 10 kmph   Therefore,  The speed of the stream = speed of downstream - speed of upstream2=5 kmph

Answer: D) Element Explanation: A substance that cannot be decomposed (broken down) into simpler substances by ordinary chemical means. Examples: gold, iron, carbon, hydrogen, oxygen, nitrogen. Material composed of only one kind of matter throughout (same atoms or same molecules).

Answer: C) Both A & B Explanation: Covalent bonds hold atoms together because the attraction between the positively charged nuclei and the negatively charged shared electrons is greater than the repulsions between the nuclei themselves.