Each Sunday, Mario weighs himself. Here are his weight changes over a 4-week period.

Week 1 2 3 4
Weight Change –1.8 +0.9 –1.4 +0.4


How much has Mario's weight changed over the entire 4 weeks?

A.
1.9 pounds

B.
–4.5 pounds

C.
–1.9 pounds

D.
4.5 pounds