What is a bacteriophage?

Which method exhibits faster growth compared to callus culture?

The Lassaigne’s extract is boiled with dil. $HNO_3$ before testing for halogens because

For the reaction sequence given below, the correct statement$(s)$ is$($are$)$
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$($In the options, $X$ is any atom other than carbon and hydrogen, and it is different in $P , Q$ and $R )$

The points $A(a, 0)$,$B(0, b)$,$C(c, 0)$,and $D(0, d)$ are such that $ac = bd$ and $a, b, c, d$ are all non-zero. Then the points:

Which of the following organisms possesses a cell wall?