Which of the following statements places a shared lock on at least a portion of a table

Question:

Which of the following statements places a shared lock on at least a portion of a table named HOMEWORK10?
a. SELECT * FROM homework10 WHERE col2 IS NULL FOR UPDATE;
b. INSERT INTO homework10 (col1, col2, col3) VALUES (‘A’, ‘B’, ‘C’);
c. UPDATE homework10 SET col3 = NULL WHERE col1 = ‘A’;
d. UPDATE homework10 SET col3 = LOWER (col3) WHERE col1 = ‘A’;
e. all of the above