The stem asks which of the four is not built up through experience. Acquired sources of motivation are those that a learner develops through upbringing, repetition and life among other people, as against the natural sources that are present from birth.

Rules laid down by the community are learnt as a child grows up among others and differ from one society to another. Lasting feelings organised around a person or an object are formed slowly through repeated emotional dealings with that person or object. Strength of will is trained by holding to a chosen purpose again and again. All three therefore belong to the acquired group.

The ductless structures that pour their secretions into the blood during fear, anger and excitement are part of the body a child is born with. Their working is bodily and automatic, so the motivating force that arises from them is natural and is not gained through experience at all.

emotional glands option is correct.