Read the passage. From “An Episode of War” by Stephen Crane The lieutenant was frowning and serious at this task of division. His lips pursed as he drew with his sword various crevices in the heap, until brown squares of coffee, astoundingly equal in size, appeared on the blanket. He was on the verge of a great triumph in mathematics, and the corporals were thronging forward, each to reap a little square, when suddenly the lieutenant cried out and looked quickly at a man near him as if he suspected it was a case of personal assault.
Which clause shows that the story’s events are changing?

A ) his lips pursed

B ) the corporals were thronging forward

C ) suddenly the lieutenant cried out

D ) the lieutenant was frowning and serious