For a Series or DataFrame object, which of the following options is incorrect?
选项：

A:The isnull() method can be used to determine missing values.;
B:The drop() method can be used directly to delete missing rows.;
C:The fillna() method can be used to fill missing rows.;
D:The fillna() method can be specified by the parameter of method to fill in missing values with the first non-missing value above or below.