IMO (A) is the answer

(1) says that BDis also of length 6. Because angle DAB = angle ABD because ( angle DAB + angle ABD + angle ADB = 180 so x + angle ABD + 180 - 2x = 180, so angle ABD = x and the triangle ABD is isosceles). But triangle BCD is isosceles too so BC = BD = 6 and this is suff

(2) insufficient because that structure can be as small as a bacteria when seen under a microscope and as large as the size of our galaxy and beyond if only the angles are known so we can never tell the length of any side

IMO A
same reasoning as above

@Farooq.
You can look into this link for a detail explanation

https://www.beatthegmat.com/gmatprep-pra ... t1615.html

Keep Rocking,
Prasant.