How did Japanese soften up Singapore(ASAP)

The first Japanese troops landed in Singapore via the northwestern coastline on 8 February 1942. After a week of intense fighting, the British Lieutenant General Arthur E. Percival surrendered Singapore to the Japanese forces under the command of Lieutenant General Tomoyuki Yam as hita.

d. japan's attack on pearl harbor

answer; (d) i believe that the correct answer is americans finally ran out of ammunition;