Question

Sometimes an economy cannot grow because of external factors, such as

lack of skilled labor.
poor infrastructure.
low domestic demand.
low demand for exports.

Answer 1

If you mean “external” as coming from outside the country, then of your four items only "low demand for exports" is a clearly external constraint. The others are internal/domestic constraints:

- Low demand for exports — external. It depends on foreign buyers, world prices and global growth; recessions abroad, trade barriers, or commodity price falls reduce export demand.
- Lack of skilled labor — internal. It reflects domestic education, training and labor-market policies (though it can be worsened by brain drain or mismatching with global skill requirements).
- Poor infrastructure — internal. This is about domestic public and private investment in transport, power, telecoms, etc.
- Low domestic demand — internal. Driven by household incomes, fiscal/monetary policy, confidence and distribution of income.

Notes:
- Some factors sit between internal and external (e.g., skill shortages aggravated by emigration or global certification requirements; infrastructure gaps worsened by lack of foreign finance).
- Policy responses differ: external problems need trade diversification, export promotion, currency and macro policies, and international cooperation; internal problems require education and training, infrastructure investment, and demand-side policies.