People have been growing chrysanthemums（菊花）for more than 2,000 years. Mums make bright and colorful gardens. People in China and other Asian cultures make tea with the flowers.
One basic kind of mum is the garden mum. The other basic kind is the florist mum. The garden mum is better able to handle different growing conditions.
There are many varieties of mums. The decorative mum is often seen in gardens. Another popular type, the quill mum, has long, straight petals（花瓣）like a tube or needle.
Chrysanthemum blooms can be white, yellow, gold, red or other colors. The plants often grow one meter high.
The soil for chrysanthemums should be kept moist but well drained so it does not get too wet.
Newly-planted mums should be watered two or three times a week, depending on conditions. Plants established in the ground may do well just with normal rainfall.
Mums grow best in full sunshine. They produce colorful blooms when days get shorter and nights get longer. The life cycle of the plant depends on the amount of daylight. This is why experts advise against placing mums near night lights or street lights. The light may interfere with their normal growth cycle. The plants may develop buds too soon.
In climates where temperatures fall below freezing, plant mums at least six weeks before the first frost. That way, the plants will be well established for cold weather.
Some gardeners say the most beautiful presentation comes from planting mums close together. But be sure to leave enough space to let air flow between the plants. If not, there may be a greater chance of disease.
To get more blooms, gardeners pinch（掐）back the branches when new growth has reached fifteen centimeters. Squeeze about five to seven centimeters off each branch. Pinch it again when a branch grows another twelve to fifteen centimeters. Stop the pinching about one hundred days before you want the plants to bloom.
What has a great effect on the life cycle of the mum?

A．The conditions of the soil.	B．The amount of daylight.
C．The amount of rainfall.	D．Cold weather.

Why do gardeners pinch back the branches when new growth reaches certain length?

A．To make mums grow thick.	B．To get more blooms.
C．To prevent mums from falling ill.	D．To let air flow between the plants.

Which of the following is true according to the passage?

A．Growing mums has a very long history and all the people in the world like making tea with mums.

B．Mums can grow one meter high and the closer they are planted, the higher they grow.

C．Though planting mums close together can make them look more beautiful, enough space should be left.

D．The petals of mums are long and straight and the more water mums get, the more quickly they grow.