The September 11 terrorist attacks completed ______ years in 2019 ?

a) 17
b) 19
c) 20
d) 18

The 18th anniversary of the September 11 terror attacks on the World Trade Centre was commemorated on September 11, 2019. The attacks were one of the worst terrorist attacks on American soil, as four-passenger airliners were hijacked by militants and two of the planes were crashed into the twin towers of the World Trade Centre in New York, US.