A mouse!

"Professor Singh finds you exceptional, so he wants you to be his apprentice. Of course, this is only an offer, and it's still your choice if you want to accept it." 

That was what Allison said. 

Penny's eyes widened upon hearing this. She simply solved one equation using the simplified method. Her thoughts, however, halted as she assessed Allison's eyes.

Allison carried a look of reluctance, expected from a mother who still wanted to care for her child. At the same time, she was trying to be supportive of her. 

"Well, we're not in a hurry," Allison smiled. "Take as much time as you need to decide and until then, I'll take care of you a bit more."

Allison tucked her daughter in and kept the night lamp open. When Penny began to breathe deep breaths, she kissed her forehead and stroked her hair. 

When Allison left, Penny slowly opened her eyes.

"Wow…" she was in disbelief. "I am being permitted to leave this house."