China on Wednesday asked Pakistan to get to the bottom of the April suicide attack that killed three Chinese nationals at the Karachi University, a day after authorities in Sindh province claimed to have arrested the mastermind and pointed finger at an unnamed neighbouring country.A burqa-clad woman suicide bomber from the banned Baloch Liberation Army BLA on April 26 blew herself near a van carrying Chinese nationals outside Karachi Universitys Confucius Institute.