Given the task definition and input, reply with output. In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

[header] How to grow sweet onions [title] Aim to plant in early to mid spring. [step] Your onions will have the best chance if they're grown in loose, fertile, and well-draining soil with a ph between 6.0 and 6.8. Use a tiller to break up the soil in the garden bed. <sep> (A) In mature plants, the soil will also contain ample seeds and roots. [title] Choose a location in your garden with minimal direct sunlight. (B) Spread 2 inches (5 cm) of mature compost or aged manure over the garden bed and work it into the soil with the tiller. [substeps] You can test the ph of the soil with a home soil test kit or with a ph meter. (C) [substeps] Don't apply this fertilizer if you're growing tomatoes, cabbage, turnips, radishes, peppers, potatoes, or mangoes. [title] Keep the soil ph below 7.5. (D) Most of the time, the soil you plant is loamy; however, if you can't find this, you may have to move it to a pot with nutrient-rich soil. [substeps] You can transfer the roots of your onion plant to a hoe for deeper growing.
B