A.
create table tscore (…, score numeric(18,1),… constraint score>=0)
B.
create table tscore (…, score numeric(18,1)>=0,… )
C.
create table tscore (…, score numeric(18,1),… constraint ck_score check(score>=0))
D.
create table tscore (…, score numeric(18,1),… constraint ck_score score>=0)