Answer: D) Covalent- network Explanation: Graphite is a covalent-network type of crystalline solid.   There are two main categories of solids. 1. Crystalline solids and 2. Amorphous solids. Crystalline solids are those in which the atoms, ions, or molecules that make up the solid exist in a regular, well-defined arrangement. There are four types of crystalline solids : Ionic solids :— Made up of positive and negative ions and held together by electrostatic attractions. They’re characterized by very high melting points and brittleness and are poor conductors in the solid state. An example of an ionic solid is table salt, NaCl. Molecular solids :— Made up of atoms or molecules held together by London dispersion forces, dipole-dipole forces, or hydrogen bonds. Characterized by low melting points and flexibility and are poor conductors. An example of a molecular solid is sucrose. Covalent-network (also called atomic) solids :— Made up of atoms connected by covalent bonds; the intermolecular forces are covalent bonds as well. Characterized as being very hard with very high melting points and being poor conductors. Examples of this type of solid are diamond and graphite, and the fullerenes. As you can see below, graphite has only 2-D hexagonal structure and therefore is not hard like diamond. The sheets of graphite are held together by only weak London forces! Metallic solids :— Made up of metal atoms that are held together by metallic bonds. Characterized by high melting points, can range from soft and malleable to very hard, and are good conductors of electricity.

Answer: A) 24 Explanation: Given that the month begins on a Friday and has 31 days   Sundays = 3rd, 10th, 17th, 24th, 31st=> Total Sundays = 5   Every second & fourth Saturday is holiday. 2nd & 4th Saturday in every month = 2   Total days in the month = 31   Total working days = 31 - (5 + 2) = 24 days.

Answer: D) 1950 Explanation: 1950

Answer: A) 0 deg C Explanation: The freezing point of water and melting point is 0 °C or 32 °F. The temperature may be lower if supercooling occurs.

Answer: D) All the above Explanation: The central nervous system CNS is responsible for integrating sensory information and responding accordingly. It consists of two main components::  1. The brain  2. The spinal cord The brain is the center of our thoughts, the interpreter of our external environment, and the origin of control over body movement. The brain can be divided into four main lobes: temporal, parietal, occipital and frontal.   The spinal cord serves as a conduit for signals between the brain and the rest of the body.

Answer: C) Tissue development Explanation:

Answer: A) not less than 60 deg Explanation: Potentially hazardous foods are foods that might contain food poisoning bacteria and are capable of supporting growth of these bacteria or formation of toxins to levels that are unsafe for consumers, if the foods are not stored at correct temperatures. Toxins are poisonous chemicals produced by some types of bacteria. The food can be left at room temperature until it reaches 60 deg C because food-poisoning bacteria will not multiply at 60 deg C or above. However, do not leave food cooling at room temperature unless you are sure that the temperature of the food is still at least above 60 C.

Answer: A) 49 kmph Explanation: Speed of the train relative to man = (125/10) m/sec = (25/2) m/sec. [(25/2) x (18/5)] km/hr = 45 km/hr. Let the speed of the train be 'x' km/hr. Then, relative speed = (x - 4) km/hr. x - 4 = 45 => x = 49 km/hr.