Deficiency of which vitamin cause the disease beri-beri?

Explanation

The structure of `Na_(2)S_(2)O_(3)` is as follows :
`overset(+)(N)aoverset(-)(O)- underset(O)underset(||)overset(S)overset(uarr)(S) - overset(-)(O) N overset(+)(a)`
The S atom which is bonded with another sulphur by co-ordinate bond has oxidation number = -2
Let the oxidation number of another S be x.
`{:(+1,,x,,-2,,-2),(Na_(2),,S,,S,,O_(3)),((+1 xx 2),+,x,+,(-2),+,(-2 xx 3)=0):}`
2 + x - 2 - 6 = 0
x - 6 = 0
`therefore` oxidation numbers of S in `Na_(2)S_(2)O_(3)` are -2 and +6.