Questions

In the early 20th century, the Balkans were called a "powder keg" because the political situation in the region was very unstable. For a long time, the Ottoman Turks occupied the balkans, and with the rise of nationalism, some balkan states declared independence.

They are teeth. 

Julian Assange

A microscope is an instrument that magnifies objects. Cells that were first observed by Robert Hooke in the year 1665 in the compound microscope.

Tetrad is a homologous chromosome pair in the given options. A homologous chromosome pair is a pair of chromosomes one from father and one from mother that has same gene sequence after the process of meiosis.

Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell. By sharing their outer most (valence) electrons, atoms can fill up their outer electron shell and gain stability.

Examples of compounds with covalent bonds ::

HCl, CO2, O2,...