In which features does Gnetum differ from Cycas and Pinus showing affinities with angiosperms?
A. Perianth and two integuments
B. Embryo development and apical meristem
C. Absence of resin ducts and leaf venation
D. Presence of vessel elements and absence of archegonia

Hint: Unlike other gymnosperms, Gnetnum possesses vessel elements in xylem which are characteristic of angiosperms whereas Cycas and Pinus lack vessel elements.

Complete answer: In angiosperms, there are vessel elements in xylem, which is present in Gnetum and absent in Cycas and Pinus. Gnetum has leaves in reticulate venation which shows an angiosperm character. The female gametophyte in Gnetum is only partially cellular before fertilization and is completely cellular only after fertilization, as archegonia are absent some of the free nuclei act as an egg, whereas archegonium is present in Cycas and Pinus.

Additional information: Gnetum is a genus of gymnosperms, the only genus in the family Gnetaceae, and order Gnetales. They are humid evergreen trees, shrubs, and lianas. Unlike other gymnosperms, they have vessel elements in the xylem.
Some species have been proposed to have been the first plants to be insect-pollinated as their fossils present in association with extinct pollinating scorpionflies.

Hence, the correct option is ‘D’

Note: Cycas, Pinus, and Gnetum belong to the gymnosperms as they do not produce flowers. Gnetum shows an affinity towards angiosperms due to the presence of an element vessel and the absence of archegonia.