( A ) $C_3$ plants respond to higher temperatures with enhanced photosynthesis while $C_4$ plants have much lower temperature optimum
( B ) Light saturation for $CO_2$ fixation occurs at 10% of full sunlight
( C ) Tomato is a greenhouse crop which can be grown in $CO_2$-enriched atmosphere for higher yield
( D ) Increasing atmospheric $CO_2$ concentration up to 0.05% can enhance $CO_2$ fixation rate
