Questions

You have to consider three things.

1. First, are the bonds polar?

Look at differences in electronegativity and if  it is >0.5, bonds are polar.

2. Second, does the molecule have unshared electron pairs?

If so, they generally lead to a polar molecule.

3. Third, is the molecule symmetric?

If so, then although the bonds may be polar, the symmetry cancels out the individual bond polarity and the molecule is non polar.

CF4 follows all the rules above and has a symmetric distribution of charge, making it nonpolar. The others all have asymmetric charge distributions.

Hence, CF4 represents a Non-polar molecule.

Fuse Wire is Made of an alloy of Tin and Lead.

If too high a current flows, the element rises to a higher temperature and either directly melts, or else melts a soldered joint within the fuse, opening the circuit. Thefuse element is made of an alloy of Tin and Lead to provide stable and predictable characteristics.

Savannas are home to a wide diversity of animals.

Many animals of the savanna migrate throughout the year, searching for food and water. Many of the droughts are seasonal and hit one area before another, so animals are constantly following the rains.

Hence, Rain fall is what often governs animal migration on savannas.

No news is good news.

Nickel

Sharjah, the city of United Arab Emirates (UAE), has been designated as the UNESCO World Book Capital 2019 by Irina Bokova, the Director-General of UNESCO, at the Headquarters of the International Federation of Library Associations (IFLA) at La Haye. The honour is in recognition of the Emirate’s pioneering role in supporting and expanding the local and regional publishing industries, promoting reading to become an intrinsic cultural practice, as well as embracing inter-cultural, knowledge-based dialogue. Sharjah was the first emirate in UAE to establish a formal school and a library. It was also the first emirate to house many cultural institutions like the Emirates Publishers Association and the Emirates’ writers Union. Sharjah is the 19th city to become World Book Capital. It is preceded by Conakry in 2017 and Athens in 2018.