Answer:
D. Aptitude is a person’s potential to learn new skills.
Step-by-step explanation:
A. Aptitudes are ability, and skills are the potential.
B. Aptitudes can be learned or trained, unlike skills.
C. Aptitude is the level of skill that a person has gained.
D. Aptitude is a person’s potential to learn new skills.
Out of the above four, the A and B part is wrong and the rest of the options are right. Skills are the ability and aptitude is the potential, and the aptitude is the level of skill which person has gained, as well as Aptitude, is the Person's potential to learn new skills. However, D is adequate, and C can be derived out of it, as if someone has potential, the better level of skills he/she will gain. Hence, D is the correct option.