Tom never dreamt of__a chance for him to be sent abroad soon.A.having B.there being

of后如果接having a chance后面就不用for him了.
there being a chance for him to be...
本结构的本来是
there was a chance for him to be sent abroad soon
dream of 后不能接that从句,所以就用there being结构（这个其实是动名词的复合结构充当宾语）
None would dream of there being such aplace.
——of的后头本来要接的是“there was such a place.”