Tomatoes are common in daily life.Cathie Martin，British scientist，has been working on developing purple tomatoes for years.Though the color is unusual，now this special kind of tomatoes has very high levels of antioxidants（抗氧化劑）.
Antioxidants，also known as AOS，are found naturally in plants like blueberries and red cabbage.Scientists believe AOS may help prevent heart disease and help fight against diseases like diabetes.But tomatoes naturally only have a small amount of AOS in them.Martin wanted to see if she could create tomatoes with lots of AOS by changing the DNA of a tomato plant.
A plant developed from specially created DNA is known as a GMO.Martin added two genes（基因）from a plant called snapdragon.Soon her plants were producing small purple tomatoes with lots of AOS.Even better，the tomatoes remained fresh almost twice as long as normal tomatoes.Martin and other scientists further tested the tomatoes on mice that were likely to get cancer.The mice that were fed the purple tomatoes lived about 30% longer than those fed normal tomatoes.Though that's good news，experiments on mice don't always predict what effects on humans will be like.We need to see more experiments about it.
GMOs were first allowed in America in the late 1990s.But GMO products weren't popular with customers.Many people were scared by the idea that the foods weren't natural or safe.There're still questions about the effects of GMO crops on the environment.However，scientists deny these claims.
Even
so，many people have concerns about them.Because of these concerns，most GMO products created over the last 20 years have focused on helping farmers rather than attracting customers.
Anyway，on September 7，2022，the US approved the purple tomatoes，which is the first time it has approved a GMO plant designed to target human health.
（1）What makes purple tomatoes really special？
A
A
A．Their medical value.
B．Their delicious flavor.
C．Their proper size.
D．Their pleasant color.
（2）What's the author's attitude to the test on the mice？
B
B
A．Favorable.
B．Doubtful.
C．Concerned.
D．Opposed.
（3）What does the underlined word "so" in Paragraph 5 refer to？
D
D
A．The environment affects GMO foods.
B．The customers do not like GMO foods.
C．GMO products are used to help farmers.
D．Scientists think GMO products are safe.
（4）What's the suitable title for the text？
B
B
A．Different DNA Can Benefit Plant Growth.
B．Tomatoes with Changed DNA Are Approved.
C．Scientists Are Changing DNA of Tomatoes.
D．Human Health Depends on Changed DNA.
