Answer: A) Uracil Explanation: Uracil is not found in DNA but found in RNA.

The sperm cell is the smallest cell in the human body. The volume of these cells is quite tiny. The head of a sperm cell is roughly 4 micrometres long, about the same size as a red blood cell (RBCs). Egg cells are the biggest cells in the human body (ovum).

Answer: A) 21 Explanation: The given number series follows a pattern that, 19 + 12 = 20 (not 21)20 + 22 = 2424 + 32 = 3333 + 42 = 4949 + 52 = 74    Hence, the odd number in the given number series is 21.

Answer: C) Convex Explanation: Convex mirror is used as rear view mirror in vehicles. Because the image is smaller, more image can fit onto the mirror, so a convex mirror provides for a larger field of view than a plane mirror. This is why they are useful.

Answer: A) Dragon flies Explanation: Dragon flies have legs but they cannot walk.

Answer: A) TRUE Explanation: Air or gas can build up in the pleural space and when this happens, it's called a pneumothorax. Hence the given statement is TRUE.

Answer: A) a pair of scissors Explanation: Any of the basic mechanical devices for applying a force are called simple machines. There are 6 basic simple machines; the lever, the wheel and axle, the inclined plane, the wedge, the pulley, and the screw. Several of these simple machines are related to each other. But, each has a specific purpose in the world of doing work.