17D Space station launched on M ay14 1973 by the US, occupied for 171 days and 13 hours by 3 missions. (6) (s?yl?b21d Hard lightweight element of the alkaline-metal group chemically magnesium, used toicontrol the speed of neutrons in nuclier reactors. (9) (?er?yl????) 25d Prinipal currency unit of Bhutan, devided into 100 Chetrum (8) (?g??????)