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 exercise to prevent blood clots [title] Get up and move around. [step] Whether you're traveling by train, plane, or automobile, long-distance travel involves a lot of sitting. When you sit, you decrease circulation in your legs-especially if you sit with your legs crossed or with one foot under you. <sep> (A) If you are on a train or coach, the seat underneath you always feels flat, as if you are sitting. While there are good ways to stretch out your legs, there is not a lot a group of people can do. (B) This will help promote blood circulation to your feet. It will also keep you from rubbing your legs in an annoying manner-you can't promote blood flow when you're sitting on one leg. (C) [substeps] You can exercise while you drive or driving, although getting up and down on the exercise train can significantly improve circulation. You can also listen to music while you exercise, which will also help to prevent blood clots. (D) [substeps] If you're on a plane, try to get an aisle seat so you can get up and move around more easily. Ideally, you want to get up and stretch your legs or walk up and down the aisle once every hour or so.
D

[header] How to plant switchgrass [title] Pick a switchgrass variety. [step] If you look for switchgrass at your local nursery you may just find a plant that's labeled " switchgrass, " but there are actually several varieties that differ in color and size. Switchgrass blooms for almost half the year, and during the winter and spring it's usually brown. <sep> (A) [substeps] Magnolia trees produce about 50% of the moisture. Maple trees produce 50% of the moisture per year. (B) Both varieties of switchgrass produce pretty stunning flowers, unique patterns, and flowers. Most also have phlebotomists at the planting areas where it grows. (C) These are factors to keep in mind when you're choosing a variety for your garden. Here are a few types commonly grown in home gardens : [substeps] Northwind: grows four to six feet tall and produces yellow blooms. (D) Pine needles will establish a base that's ready for planting a newer, more established fire from. [substeps] Switchgrass colors for more variety can also be found at a garden center or online.
C

[header] How to track tornadoes [title] Watch doppler radar for severe storm cells. [step] Doppler radar detects the speed and movement of a storm by using radio wave pulses and it is highly accurate. There are different colors to signify the intensity of a storm. <sep> (A) [substeps] Doppler radar does not detect larger goose bumps, compared to doppler radar in humans. Doppler radar maps use higher frequency signals and are written to better identify an object than radar charts. (B) Greens indicate light rain, yellows and oranges are moderate to heavy rains, and red means very heavy rain or hail. [substeps] Use a weather app on your phone, visit weather websites like weather.com and weather underground, or watch your local news for up to date doppler forecasts. (C) [substeps] Doppler radar radar does not fire at specific types of people. Telethycline repelled asleep minutes before a storm appeared. (D) [substeps] Tornadoes usually report telling you the direction of megaheros. This message will be in your radar's dialogue box after it summarizes the storm status.

B