What is the 'Warburg effect' on photosynthesis?

Photorespiration occurs:

Given below are two statements:
Statement $I$: In $C_3$ plants,some $O_2$ binds to $RuBisCO$,hence $CO_2$ fixation is decreased.
Statement $II$: In $C_4$ plants,mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration.
In the light of the above statements,choose the correct answer from the options given below:

Which condition is favorable for photorespiration?

Photorespiration takes place in which of the following cell organelles?

Assertion : Under conditions of high light intensity and limited $CO_2$ supply,photorespiration has a useful role in protecting the plants from photo-oxidative damage.
Reason : If enough $CO_2$ is not available to utilize light energy for carboxylation to proceed,the excess energy may not cause damage to plants.