Which structure of $RNA$ resembles a cloverleaf?

The $A/U$ and $G/C$ ratio in $RNA$ is:

The term '$RNA$ world' was coined due to which research finding in the $1980s$ regarding evolution?

$A$ ribozyme is ...

Which $RNA$ has the shortest lifespan?

Given below are two statements:
Statement $I$: In the $\text{RNA}$ world,$\text{RNA}$ is considered the first genetic material evolved to carry out essential life processes. $\text{RNA}$ acts as a genetic material and also as a catalyst for some important biochemical reactions in living systems. Being reactive,$\text{RNA}$ is unstable.
Statement $II$: $\text{DNA}$ evolved from $\text{RNA}$ and is a more stable genetic material. Its double helical strands being complementary,resist changes by evolving a repairing mechanism.
In the light of the above statements,choose the most appropriate answer from the options given below: