In relation to the multiple choice question, we know that (a)...

In relation to the multiple choice question, we know that (a) and (c) didn't happen because they would have been compelled to lodge a change of susbstantial or ceasing substantial. Note that shorting is selling, so there isn't much difference between these choices except for lodging collateral and paying borrow fees. The extension of (c) into creating a net short position is not possible in the fund that holds the vast majority of BLK's interest in GXY as that fund prohibits net short (ie, it is a long only fund). The fund could partially have done (d), which is to say it could have traded in and out of the stock, subject to not moving by more than 1% of shares on issue or falling below 5% as it would have had to lodge change in substantial notices each time.

I've no idea whether (b) occurred, but given the very small proportion of the fund being comprised by GXY, my guess is that the manager had more important things to worry about. You can google the Blackrock World Mining Fund annual report to find some information on holdings and other things (reported with a lag).