Which of the following enzymes is used for joining $DNA$ fragments?

In a haplontic life cycle,how many of the four haploid nuclei degenerate?

The angle between the lines $\vec{r}=(2 \hat{i}-3 \hat{j}+\hat{k})+\lambda(\hat{i}+4 \hat{j}+3 \hat{k})$ and $\vec{r}=(\hat{i}-\hat{j}+2 \hat{k})+\mu(\hat{i}+2 \hat{j}-3 \hat{k})$ is

The displacement-time graph for two particles $A$ and $B$ are straight lines inclined at angles of $30^o$ and $60^o$ with the time axis. The ratio of velocities of $V_A : V_B$ is

$A$ point object is placed at a distance of $30 \, cm$ from a convex mirror of focal length $30 \, cm$. The image will form at

The collector plate in an experiment on the photoelectric effect is kept vertically above the emitter plate. $A$ light source is turned on,and a saturation photocurrent is recorded. An electric field is then switched on,which has a vertically downward direction.