The world's most problematic aquatic weed is:

Parthenocarpic fruit is

The number of subsets of $\{1, 2, 3, \ldots, 9\}$ containing at least one odd number is

In a standing wave on a string rigidly fixed at both ends:

$A$ body cools from $62^{\circ}C$ to $50^{\circ}C$ in $10$ minutes and to $42^{\circ}C$ in the next $10$ minutes. The temperature of the surrounding is ........... $^{\circ}C$.

The floral formula (image) is that of