Answer: A) Laser Explanation: Compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony and released in 1982.  These are actually made to replace floppy disks that were used to store files and programs from the computer.   The format was originally developed to store and play only sound recordings but was later adapted for storage of data (CD-ROM).   These CD's uses Laser technology.

Answer: A) copper(II) hydroxide Explanation: Sodium chloride: The solubility rules tell you that all halides are soluble with the exception of those formed with siver, mercury, and lead ions. Since this is not the case here, sodium chloride will be soluble.   Silver nitrate: It is soluble because all nitrates are soluble, without exception.   Potassium sulfate: It is soluble because all sulfates are soluble with the exception of those formed with silver, calcium, barium, mercury, lead, and strontium ions.   Copper (II) hydroxyde: It is insoluble because all hydroxides are insoluble with the exception of those formed with alkali metal ions and barium.

Answer: B) Sarcomere Explanation: The myofibrils are composed of actin and myosin filaments, repeated in units called sarcomeres, which are the basic functional units of the skeletal muscle.

Answer: A) Garba Explanation:

The reciprocal of a negative number is always a negative number. So that the number and its reciprocal multiply to 1.    All real numbers except 0 have reciprocals.

Mercury was the remedy of choice for syphilis in Protestant Europe. Until the early 20th century, the primary treatment for syphilis was mercury, in the form of calomel, ointments, steam baths, pills, and other concoctions. Mercury was already being used in Western Europe to treat skin diseases.

Answer: B) a surface exposed by a retreating glacier Explanation:

Answer: D) All the above Explanation: Common properties of Minerals are :   1. All minerals are formed in a natural process. 2. Minerals are inorganic 3. Minerals are crystalline solids. 4. Every mineral is an element or compound with a definite chemical composition.