whAt possiBly rEsultED in thE Evolution From lEAFlEss trEE to FlAt lEAvEs
A．thE DECrEAsE Co₂ in lEvEls.
B．thE inCrEAsE oF ForEsts.
C．thE Drop oF tEmpErAturEs.
D．thE ChAngE oF ClimAtEs likE toDAy.