在缺省用户目录下创建一个新用户alex的Linux命令是(62)。A.useradd -d /home/alex alexB.useradd -d /usr/alex alexC.useradd -D /home/alex alexD.useradd -D /usr/alex alex

在缺省用户目录下创建一个新用户alex的Linux命令是（）

A.useradD. -d/home/alex alex
B.useradD. -d/usr/alex alex
C.useradD.-D/home/alex alex
D.useradD.-D/usr/alex alex

请阅读短文，完成第小题。
One evening, while Marcos Ugarte was doing his homework and his father, Eduardo, prepared lesson plans, they heard someone yelling outside. Eduardo,47, and Marcos,15, stepped onto the porch of their home in Troutdale, Oregon, and saw a commotion four doors down, outside the home of their neighbors, the Ma family."I didn't think anything was wrong," Eduardo recalls."! Told Marcos we should give them some privacy." He headed back inside, but Marcos's eye was caught by a glow from the Ma house.
"Dad, the house is on fire! " Marcos cried.
Clad only in shorts, the barefoot teen sprinted toward the Ma's home with his dad. Grandmother Yim Ma, mother Suzanne Ma, and son Nathan Ma were gathered on the front lawn yelling for help. When the Ugartes got there, they saw father Alex Ma stumbling down the stairs, coughing, his face black with soot.
"Is anyone else in the house?" Eduardo asked.
"My son! " Alex managed to say, pointing to the second floor. Eduardo started up the stairs, but thick, black smoke, swirling ash, and intense heat forced him to his knees. He crawled upstairs and down the hall where Alex said he would find Cody, eight, who had locked himself in a bedroom.
As the fire raged across the hall, Eduardo banged on the bedroom door and tried to turn the doorknob. Cody didn't respond. Eduardo made his way back downstairs.
Meanwhile, Marcos saw Yim and Suzanne pulling an aluminum ladder out of the garage."Cody was standing at the window, screaming for help," says Marcos."I knew I had to do something." He grabbed the ladder, positioned it near the window, and climbed toward the boy.
When Marcos reached the window, he pushed the screen into the room and coaxed Cody out."It's OK," Marcos told him. "I've got you."
Holding Cody with one arm, Marcos descended the ladder.
When firefighters arrived, plumes of black smoke were billowing from the back of the house as flames engulfed the second floor. Emergency personnel took Cody to a nearby hospital, where he was treated for smoke inhalation and released. No one else was injured. The cause of the blaze is still under investigation.
"You just don't see a teenager have that kind of?composure," says Mark Maunder, Gresham Fire Department battalion chief.
The Ma family relocated. The day after the fire, Alex visited Marcos."Thank you for saving my son." Alex said. "You are his hero forever."

Whom does the underlined word "he" in PARAGRAPH 5 refers to?__________
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A．Alex.
B．Eduardo.
C．Mareros.
D．Nathan.