Let the speed of current = 'C' km/hr

Given the speed of boat in still water = 6 kmph

Let 'd' kms be the distance it covers.

According to the given data,

Boat takes thrice as much time in going the same distance against the current than going with the current

i.e, d8 - C = 3 × d8 + C

$$\begin{gathered} ⇒ 24 - 3C = 8 + C \\ ⇒ 4C = 16 \\ ⇒ C = 4 kmph \end{gathered}$$

Hence, the speed of the current C = 4 kmph.

As the arguments C and E states that other companies are on the losing end with this scheme, it is the only appropriate answer to this question.

Osmosis is the process in which water molecules move from a region of higher water potential to a region of lower potential down a water potential gradient across a partially permeable membrane. It doen't requires any additional energy to do this work. 

So, Osmosis is a Passive.

Active and passive transport processes are two ways molecules and other materials move in and out of cells and cross intracellular membranes.

1. Active transport is the movement of molecules or ions against a concentration gradient (from an area of lower to higher concentration), which does not ordinarily occur, so enzymes and energy are required.

2. Passive transport is the movement of molecules or ions from an area of higher to lower concentration. Passive transport occurs because of the entropy of the system, so additional energy isn't required for it to occur.

3. Active transport requires energy to proceed, while passive transport does not require the input of extra energy to occur.

Dry ice or Cardice is the solid form of Carbon dioxide.

1. It has an advantage of lower temperature than the water ice and doesn't leave any residue.

2. The reason why it is called as Dry ice is because unlike the normal ice, it won't melt into liquid form. It directly evaporates into the air as gas. That is Solid to gas form passing through liquid state is a phenomenon called as Sublimation.

3. The primary use of dry ice is as cooling agent.

Footsteps. 

Yes, as you walk forward, you will leave the footstep behind you.

The visible colors from Longest wavelength to Shortest wavelength are :: Red, Orange, Yellow, Green, Blue and Violet.

                    Red > Orange > Yellow > Green > Blue > Violet.

1. Infrared radiation has a longer wavelength than visible Red light.

2. Ultraviolet radiation has a shorter wavelength than the visible violet light. 

3. The white light is a mixture of the colors of the visible spectrum.

Lithoshpere are composed of rocks in the crust and upper mantle that behave as brittle solids. The lithosphere is Earth's outermost layer.

Here the given series 7, 11, 19, 35, ?

follows a pattern that (x 2 - 3) i.e,

7

7 x 2 - 3 = 11

11 x 2 - 3 = 19

19 x 2 - 3 = 35

35 x 2 - 3 = 67

67 x 2 - 3 = 131

Hence the next number in the given number series is 67.