How many integuments surround the ovule in $Pinus$ and $Cycas$?

$A$ person walks along a straight road from his house to a market $2.5 \ km$ away with a speed of $5 \ km/h$ and instantly turns back and reaches his house with a speed of $7.5 \ km/h$. The average speed of the person during the time interval $0$ to $50 \ min$ is (in $m/s$):

Let $A$ and $B$ be two symmetric matrices of the same order. Then,the matrix $AB - BA$ is

What type of sugar is glyceraldehyde?

When a current of $2\, A$ flows in a battery from negative to positive terminal, the potential difference across it is $12\, V$. If a current of $3\, A$ flows in the opposite direction, the potential difference across the terminals of the battery is $15\, V$. The $emf$ of the battery is ............... $V$.

The Gibbs energy for the decomposition of $Al_2O_3$ at $500^o C$ is as follows :
$\frac{2}{3} Al_2O_3 \rightarrow \frac{4}{3} Al + O_2, \Delta G = +966 \ kJ \ mol^{-1}$
The potential difference needed for electrolytic reduction of $Al_2O_3$ at $500^o C$ is at least ...... $V$.