Which of the following orders of Gymnosperms is completely extinct?

How many archegonia develop on one gametophyte of Cycas?

The number of neck canal cells in the archegonium of $Cycas$ is:

How many integuments surround the ovule in Pinus and Cycas?

Top-shaped,multiciliate male gametes and the mature seed which bears only embryos with two cotyledons are characteristic features of which of the following?

Three generations one within the other are present in the seeds of