C4 pathway and photorespiration

In $C_3$ plants RuBisCO also acts as an oxygenase: when $O_2$ binds to it, RuBP is broken down in photorespiration, which fixes no $CO_2$, forms no ATP or NADPH and releases already fixed $CO_2$. This lowers productivity.
In $C_4$ plants $CO_2$ is first fixed in the mesophyll cells by PEP carboxylase into a $C_4$ acid, which is transported to the bundle sheath cells and decarboxylated there.
This raises the $CO_2$ concentration around RuBisCO in the bundle sheath, so RuBisCO works as a carboxylase and its oxygenase activity is minimised.
As a result photorespiration does not occur (is negligible) in $C_4$ plants, so their productivity and yields are better; they also tolerate higher temperatures and high light intensities.
Hence $C_4$ plants are more efficient due to a lower rate of photorespiration.
Note: the answer line in the source PDF prints (3), but its own explanation ('Photorespiration does not occur in C4 plants') and NCERT support 'lower rate of photorespiration', which is taken as the answer here.

In $C_3$ plants the enzyme RuBisCO also binds $O_2$ and carries out photorespiration, in which fixed carbon is lost as $CO_2$ without the production of ATP or sugar. This lowers the efficiency of photosynthesis.
$C_4$ plants have Kranz anatomy. In the mesophyll cells $CO_2$ is first fixed by PEP carboxylase, an enzyme that has a very high affinity for $CO_2$ and does not react with $O_2$.
The $C_4$ acid formed is transported to the bundle sheath cells and decarboxylated there, so the $CO_2$ concentration at the site of RuBisCO becomes very high.
This makes RuBisCO work as a carboxylase and minimises its oxygenase activity, so photorespiration practically does not occur.
Any $CO_2$ that is released in the bundle sheath cells is trapped and refixed by PEP carboxylase in the surrounding mesophyll cells, so no $CO_2$ escapes from the leaf.
For the same reason the $CO_2$ compensation point of $C_4$ plants is very low (not more), and the $CO_2$ efflux is prevented (not allowed).
So $C_4$ plants are more efficient because the $CO_2$ generated during photorespiration is trapped and recycled through PEP carboxylase.