Task: Class Definition Understanding (ontology: Food_Agriculture/Crop_Ontology)

Which of the following definitions best describes 'Flag leaf length - Estimation'?

A. Observe flag leaf length and rate it.
B. Observe the surface of lemmas and record its type.
C. The presence of basal spikelets sterility on the spike and record it.
D. Observe the growth of plants per plot/entry under low temperature condition and rate the tolerance based on crop mortality or reduced growth.

Answer: Observe flag leaf length and rate it.