This is about a question Donald Trump failed to answer.

Granted, there are a lot of those, but this was a particularly tough one. Indeed, it was likely more difficult in its way than anything April Ryan or Lester Holt has ever asked him. But then, they’re only adults. Ava Rose Olsen is 7 years old.

As anyone who has experience with human beings of that age can attest, no one asks more pointed questions. And the one she posed in a letter to Trump last August was a whopper:

“I hate guns,” she explained in her little girl’s scrawl. “One ruined my life and took my best friend. I don’t want that to ever happen again. Are you going to keep kids safe? How can you keep us safe?”

The best friend she refers to is — was — 6-year-old Jacob Hall, who was shot in September 2016 on the playground of Townville Elementary School in South Carolina. Police say his assailant was a 14-year-old boy who took his father’s handgun from a nightstand, shot the man in the head, then drove to the school and opened fire, screaming, “I hate my life.”

Two others were also hit, but survived. Jacob suffered massive blood loss and died three days later. He was buried in a Batman costume. He loved superheroes.

And Ava loved Jacob. In fact, she had already told her mother that, someday, she was going to marry him. She was on that playground the day he was shot. What she saw traumatized her.

In the days and weeks afterward, Ava took to pulling out her eyelashes and hitting herself. She clawed at her own skin. And she began repeating the shooter’s words. “I hate my life,” she said.

A doctor diagnosed Ava with post-traumatic stress disorder, and her parents took her out of Townville Elementary. She’s home schooled now.

Think of that. This is now a country where even 7-year-olds have PTSD.

We are indebted to the Washington Post for its reportage on all this. This week, it published the letter Trump sent Ava just before Christmas. In it, he praised her bravery, offered his prayers and said the safety of children is his goal as president.

He said a lot of things, but he didn’t answer her question, didn’t say how he would keep her safe. Ava noticed. Last month, she sent a follow-up. In it, she thanked Trump for his prayers and offered some security ideas of her own.

One was to “move the schools to a safer area.” Another was to “have people around to make sure that nobody can hurt us.” Still another was to build school campuses in circular shapes with playgrounds in the middle, inaccessible from the street.

“Somehow,” she pleaded, “help people to understand what happens to kids like me who have seen and heard what happens when a gun hurts someone.”

In his State of the Union speech, Trump made a point of shouting out to the Second Amendment. He made no mention of the kids — 135,000 according to a Post analysis — who have experienced school shootings since the 1999 Columbine massacre. Already this year, there have been at least six such incidents resulting in injury or death. It’s February.

In a nation awash with guns, where conservative orthodoxy holds that even the most modest effort to restrain this American carnage runs afoul of the sacred Second, Ava cuts through the political babble with the directness of a child.

“How can you keep us safe?”

How, indeed?

Trump sought to deflect her fears with platitudes. But this little girl asked a serious question. She deserves a serious answer.

We all do.