41.Which of the following gases is used for regrigeration ?

42.In the process of cleaning, soap functions by : 1. changing hard water into soft water2. reducing oily and greasy dirt into colloidal particles3. converting the dirt to lather and water soluble particles 4. increasing the cleansing properties of water

43.Sun appears reddish during the rising and setting time because

44.The type of glass used in making lenses and prisms is :

45.The following are some great discoveries in Physics : 1. X-rays 2. Theory of relativity 3. Super conductivity 4. Raman effectThe chronological order in which they were discovered is