Questions

Sound is a mechanical vibration and needs a medium for propagation. The higher the density of the medium, the faster the sound travels. So, sound cannot travel through vacuum.

As the sound travels faster in solids than liquids and gases, sound travels faster in the glass than Air and water.

6 April was declared as the International Day of Sport for Development and Peace (IDSDP) by the UN General Assembly. On the occasion of the 2017 International Day of Sport for Development and Peace (IDSDP), the United Nations Office on Sport for Development and Peace (UNOSDP) launches the digital campaign #WePlayTogether to encourage organizations and individuals.

The World Health Organization is a specialized agency of the United Nations that is concerned with international public health. It was established on 7 April 1948, Headquartered in Geneva, Switzerland.

Dr Soumya Swaminathan has been appointed the deputy director general for programmes (DDP) of World Health Organisation (WHO). She also holds a key position as secretary in the department of health research, ministry of health and family welfare.

In chemistry, a metal is an element that readily forms positive ions (cations) and has metallic bonds. Metals are opaque, lustrous elements that are good conductors of heat and electricity. Most metals are malleable and ductile and are, in general, denser than the other elemental substances.

Examples of metals are aluminium, copper, iron, tin, gold, lead, silver, titanium, uranium, and zinc.

Here Se - Selenium is an element but is not a metal, S - Sulphur is not a metal and I - Iodine is also not a metal.

Hence, Zn - Zinc is the only metal in the given options.