Shared electric scooter(电动滑板车) programs have appeared in cities across the world, spreading out across sidewalks and allowing users to check them out with their phones and return them wherever they like.

The scooter programs have been controversial. Critics say they are resulting in many injuries and even deaths, and that they are becoming a new form of urban litter as they block sidewalks for pedestrians(行人). Now, a new study is introducing a new criticism targeting one of the program's main selling points ---the idea that scooters are good for the environment.

The study by researchers at North Carolina State University looks at the whole lifecycle of the vehicles---from production to disposal. Most importantly, it looks at the process of having to constantly gather and recharge the scooters. The study found that a one-mile (1.6) kilometres’ trip on an electric scooter generally produces more greenhouse gases than riding a bus.

The researchers said they decided to conduct the study after finding slogan(口号) on scooter from the company Lime saying, “your ride is carbon-free.” But that`s not the case. The scooters tend to have a short life. Some are abandoned after being broken, and there have been reports of them being thrown into rivers or canals. The producing process accounts for about half of the scooter's emissions(排放). The other half is emitted in the gathering and recharging process.

"Roughly two-thirds of the time, scooter rides generate more greenhouse gas emissions than the alternative,"the study's authors said, adding that the emissions produced by shared scooter riders are greater than car riders.

The study recommends that the programs use electric vehicles to collect the scooters--- doing so only when they are used up, reduce the distances between collection and storage points, and use more recycled materials in production in order to reduce their emissions. Requiring users to return the scooters to docks, rather than leaving them anywhere, would also greatly reduce emissions---though it would obviously reduce the scooters' convenience appeal.

Want to buy some gifts for children? See the following ones.

Wonder Crew dolls

Wonder Crew creates dolls for boys. The dolls are aimed at encouraging boys to express kindness and other characteristics not encouraged in their other toys. “I wanted to address the developmental needs of the whole child.” Wider told USATODAY. “Toys have the power to teach.”

Sale for $29.99 on Amazon.

Barbie dolls that use a wheelchair

Mattel created dolls with disabilities to inspire girls to tell more stories. Barbie expanded its Fashion line to showcase dolls in a wheelchair and a removable prosthetic leg (假肢). “We can have the conversation around physical disabilities by including them into our fashion doll line to further Show a special view of beauty and fashion,” Mattel said.

Sale for $19.99.

Dolls inspired by children with autism

Lottie Dolls offers a doll inspired by a boy with autism. The doll kit includes an astronaut’s suit and a companion dog named Cookie. Lottie Dolls, an Irish company, offers a host of dolls that highlight diversity.

Sales for $30 on Amazon.

Plastic Army Women

A 6-year-old girl wanted to play with female plastic soldiers. She got her with when Pennsylvania company BMC Toys agreed to make Plastic Army Women. When completed, a pack of 24 figurines (小塑像) will include six different poses and should be available on the company website and on Amazon. It is available for pre-order at different price points.