单选题：CIn the kitchen of my mother’s houses there has always been

CIn the kitchen of my mother’s houses there has always been a wooden stand (木架) with a small notepad (记事本)　and a hole for a pencil.
I’m looking for paper on which to note down the name of a book I am recommending to my mother. Over forty years since my earliest memories of the kitchen pad and pencil, five houses later, the current paper and pencil look the same as they always did. Surely it can’t be the same pencil?　The pad is more modern, but the wooden stand is definitely the original one.
“I’m just amazed you still have the same stand for holding the pad and pencil after all these years.” I say to her, walking back into the living-room with a sheet of paper and the pencil. “You still use a pencil. Can’t you afford a pen?”
My mother replies a little sharply. “It works perfectly well. I’ve always kept the stand in the kitchen. I never knew when I might want to note down an idea, and I was always in the kitchen in those days.”
Immediately I can picture her, hair wild, blue housecoat covered in flour, a wooden spoon in one hand, the pencil in the other, her mouth moving silently. My mother smiles and says, “One day I was cooking and watching baby Pauline, and I had a brilliant thought, but the stand was empty. One of the children must have taken the paper. So I just picked up the breadboard and wrote it all down on the back. It turned out to be a real breakthrough for solving the mathematical problem I was working on.”
This story—which happened before I was born—reminds me how extraordinary my mother was, and is, as a gifted mathematician. I feel embarrassed that I complain about not having enough child-free time to work. Later, when my mother is in the bathroom, I go into her kitchen and turn over the breadboards. Sure enough, on the back of the smallest one, are some penciled marks I recognize as mathematics. Those symbols have travelled unaffected through fifty years, rooted in the soil of a cheap wooden breadboard, invisible (看不到的) exhibits at every meal.Why has the author’s mother always kept the notepad and pencil in the kitchen? A．To leave message
B．To list her everyday task
C．To note down maths problem
D．To write down a flash of inspiratio