Pen is to Write as Knife is to ?

The process by which plants make food using sunlight is called:

A walks 15 km North, turns right walks 20 km, turns right walks 15 km, turns right walks 20 km. How far from starting point?

DNA stands for:

In a circular table of 8 people, person 1 sits opposite person 5, person 2 sits opposite person 6, person 3 sits opposite person 7. Who sits opposite person 4?

Statements: All roses are flowers. Some flowers are thorns. No thorn is a leaf. Some leaves are stems. Conclusion I: Some roses are thorns. Conclusion II: No flower is a stem. Which is correct?