Which of the following is a bactericidal antibiotic?

The oxide,which cannot act as a reducing agent,is

Match the following columns.

Column-$I$	Column-$II$
$A.$ $500$ million years ago	$1.$ Invertebrates
$B.$ $350$ million years ago	$2.$ Jawless fishes
$C.$ $320$ million years ago	$3.$ Sea weeds and few plants

The potential difference between $A$ and $B$ in the figure is .............. $V$.

The $P-V$ diagram of a system undergoing thermodynamic transformation is shown in figure. The work done on the system in going from $A$ $\rightarrow B$ $\rightarrow C$ is $50 \ J$ and $20 \ cal$ heat is given to the system. The change in internal energy between $A$ and $C$ is ...... $J$. (Take $1 \ cal = 4.2 \ J$)

The middle lamella is primarily composed of: