A: How're you going to prepare for the test?
B: Well, I'm not going to learn the grammatical rules by heart.
A: But those are exactly the things I was going to do.
B: No, you don't have to do that. The teacher is going to examine the language skills, not language knowledge.
A: Are you sure?
B: I say this for certain.
exp. Definitely or for sure. （肯定，确定）
e.g. ——How many people are coming to dinner tonight? —— I can't say for certain—my family tends to just show up without responding to invitations.
e.g.No one can say for certain how the world’s climate is likely to change.
e.g. She decided to forgo the party and prepare for the English exam.
e.g. She rolled up her sleeves and began to prepare for supper.
e.g. He went to see his favorite band in concert and knew all the songs by heart.
e.g. Why don't you write out a speech and get it by heart?
3.learn something by heart：记住，背诵，默诵
e.g. We had better learn by heart as many sentence patterns as we can.
e.g. The children all had to learn the poem by heart.
e.g. Learn this by heart.
e.g. It' s no use learning the text by heart without understanding it.