Metamorphic rocks are formed when existing rocks are changed by heat, pressure, or chemically active fluids.
The word metamorphic means:
\[
\text{changed form}.
\]
Limestone is a sedimentary rock.
When limestone is subjected to high temperature and pressure, it changes into marble.
Thus:
\[
\text{Limestone} \longrightarrow \text{Marble}.
\]
Therefore, marble is a metamorphic rock.
Sandstone is a sedimentary rock.
Limestone is also a sedimentary rock.
Basalt is an extrusive igneous rock.
Hence, among the given options, the metamorphic rock is:
\[
\text{Marble}.
\]