If stamens are arranged in two whorls with antipetalous outer whorl then the condition is

1. Obdiplostamenous
2. Diplostamenous
3. Didynamous
4. Epiphyllous

Obdiplostemonous: Having two sets of stamens in alternating whorls, with the outer whorl opposite the petals.
Diplostamenous: having two whorls of stamens, with the outer whorl opposite the sepals and the inner whorl opposite the petals.
Didynamous: Having four stamens in two pairs of unequal length
Epiphyllous: stamens attached to the perianth.

So the correct answer is 1) Obdiplostemonous.