What is crucial in our discussion on the existence of covert pied-piping is that in order for an element in syntactic islands like complex NPs and adjunct clauses to be questioned in Sinhala, the second part of the WH-word, i.e., d a , must appear at the edge of the island, not next to the first part of WH-word inside the island.
in my analysis clausal pied-piping in these languages is explained in the following way: On its way to the Spec of +WH-C, the WH-phrase will pass through the Spec of intermediate CPs due to Subjacency.