Which of the following statements is false?

A. DNA replication occurs only in S phase.
B. The activation of S-Cdk helps prevent the onset of M phase.
C. The activation of S-Cdk helps prevent DNA replication occurring more than once each cycle.
D. The activation of S-Cdk initiates DNA replication.

Explanation:

All events of cell cycle is regulated by a heterodimeric protein complex called cyclin CDKs, cyclin is the regulatory subunit which binds to CDKs and activate them whereas CDKs(cyclin dependent kinases) is the catalytic subunit where cyclin bound CDKs become active and act as serine threonine kinase and phosphorylate target proteins

The activation of S-Cdk helps prevent the onset of M phase because S phase cyclin CDK complex trigger initiation of DNA replication from pre replication complex and inhibits rebinding of components of pre replication complex

the major parts of the digestive system:

salivary glands.

pharynx.

esophagus.

stomach.

small intestine.

large intestine.

rectum.

accessory digestive organs: liver, gallbladder, pancreas.