State whether each set of hypotheses is valid for a statistical test.

a. H0H0: =0=0 vs HaHa: <0<0 [ Select ] ["Valid", "Not Valid"]

b. H0H0:p^=0.3p^=0.3 vs HaHa:p^0.3p^0.3 [ Select ] ["Valid", "Not Valid"]

c. H0H0:1212 vs HaHa:1=21=2 [ Select ] ["Valid", "Not Valid"]

d. H0H0:p=25p=25 vs HaHa:p25