Hamlet:
If you have hitherto conceal'd this sight,
Let it be tenable in your silence still,
And whatsoever else shall hap to-night,
Give it an understanding, but no tongue:
Tenable seems a strange word. I don't know if it means any of the following:
a) told outright
b) explained quietly
c) remain intact
d) kept secret
What did Shakespeare mean by tenable in this passage?