Oxygen. Is the correct answer
Oxygen has the same number of valence electrons as sulfur. An ion can be an element that gained or lost an electron.
Answer: -
Surface Tension
Explanation: -
Surface tension is cohesive force created as a result of hydrogen bonding, that enables a liquid drop to have a minimum surface area.
Due to it being cohesive, the water top surface is concave in nature, allowing us to hence slightly overfill a glass with water.
Due to surface tension, the surface of water behaves like a stretched membrane, allowing dense objects like a length wise steel needle to float on water.
Thus, the hydrogen bonding in water creates __surface tension__, a cohesive force that enables one to slightly overfill a glass with water or allows denser objects, such as a lengthwise steel needle, to float on water
The sand to pass through, but not the gravel. Hope this helps!
1) The metal which reduces the other compound is the one higher in the reactivity. So in this case it is 
.
2) The substance which brings about reduction while itself getting oxidised (that is losing electrons) is called a reducing agent. Here, $\mathrm{Zn}$ is the reducing agent and reduces Cobalt Oxide to Cobalt while itself getting oxidised to Zinc oxide.
The tilt of the earth provides the earth with seasons. As the earth revolved around the sun different portions (northern or Southern Hemisphere) is exposed more directly to the suns radiation, thus it is hotter in those regions. (Why the United States experiences winter in December but Australia experience summer in December.)
