cryptogram

""Can you keep a secret?" "Yes." "So can I.""

"The teacher encoded the secret message using a simple letter substitution. "

"The morning classes at school begin at 8:00 a.m. "

"Where he went after he left the house is a puzzle."

"The spy decoded the secret message to learn the enemy's plans. "

"The president of the student council used last year's debate as a precedent for this year's election rules. "

"My grandmother's cough syrup is a simple; it's made from just one type of herb. "

"The spy encrypted the message to keep its contents secret from the enemy. "

"He is a student of life."

"My teacher gave a message to the class about the upcoming exam. "

"The student is solving a math problem. "

"My phone's calculator showed the cipher "123" for the product of 3 times 4. "