(b) : C4 plants are photosynthetically more efficient than C3 plants because C4 plant contain two types of chloroplast i.e., bundle sheath chloroplast and mesophyll chloroplast. So such plants operate a dicarboxylic acid cycle in addition to Calvin cycle. CO2 acceptor molecule (PEP) is present in large bundle sheath cell which has higher efficiency in picking up CO2. Thus, photosynthesis continues even at low CO2 concentration and the rate of photorespiration is also negligible.