To join 'n' tables 'n-1' conditions should be satisfied.

So to join 4 tables 3 conditions should be satisfied.

In general, polar solvents dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes.
As water molecules are polar, polar molecules dissolves in water.

Oxygen in our blood is transported by a protein named Haemoglobin.

A data structure is a specialized format for organizing and storing data. General data structure types include the array, the file, the record, the table, the tree, and so on. Any data structure is designed to organize data to suit a specific purpose so that it can be accessed and worked with in appropriate ways.

Linear data structure: A linear data structure traverses the data elements sequentially, in which only one data element can directly be reached.

Ex: Arrays, Linked Lists, Stack, Queue, Any type of List all are linear.

Trees like Binary Tree, B Tree or B+ Tree are examples of non linear data structure.

All the above given statements are functions of Inventory.

Inventory or stock is the goods and materials that a business holds for the ultimate goal of resale. Inventory management is a discipline primarily about specifying the shape and placement of stocked goods.

The primary function of inventory is to use marketing and production to increase profitability, to get the maximum amount for the business' investment. There are other functions of inventory, such as balancing supply and demand, improving efficiency, establishing a safety stock and geographical specialization.

Here given that 9 = 63, 8 = 48, 7=35, ... 

The given question follows a pattern that

9 x (9 - 2) = 9 x 7 = 63

8 x (8 - 2) = 8 x 6 = 48

7 x (7 - 2) = 7 x 5 = 35

Similarly, 4 x (4 - 2) = 4 x 2 = 8.

1/2 as a percentage means

1/2 = 0.5 in decimal

Now, in percentage means 0.5 x 100% = 50%.

Groundwater is all the water that has penetrated the earth's surface and is found in one of two soil layers. The one nearest the surface is the "zone of aeration", where gaps between soil are filled with both air and water. Below this layer is the "zone of saturation", where the gaps are filled with water.