Answer: C
Explanation: The ocean floor is largely unexplored so no one knows what it is like.
Secondary succession occurs more rapidly than primary because soil is already available so there is no need for any other species. Also, there might still be surviving species in the soil present like seeds, roots and other plant organs.
Answer : The correct option is, 
Explanation :
To calculate the pressure of gas we are using ideal gas equation as:

where,
P = pressure of gas = ?
V = volume of gas = 0.046 L
n = number of moles of gas = 3.4
R = gas constant = 8.314 L.kPa/mol.K
T = temperature of gas = 298 K
Now put all the given values in the above formula, we get:


Therefore, the pressure of gas is, 
Answer:
Na₂₆F₁₁
Explanation:
We find the moles of the substance assuming 100 g of the substance is present. Why do we take 100 g? Because then the percent of sodium/fluorine, would be the g of sodium/fluorine respectively:
74.186 g Sodium | 1 mol Sodium/23 g => 3.2255 mol Na
25.814 g Fluorine | 1 mol Fluorine/19 g => 1.3586 mol F
Divide each by smallest number of moles:
3.2255/1.3586 = 2.37
1.3586/1.3586 = 1
Multiply by common number to get a smallest whole number:
2.37*11 = 26,
1*11 = 11
The empirical formula is Na₂₆F₁₁