Topic 1: Increasing travels between countries enable people to learn different cultures or to increase tension between people from different countries

Stressful + activity, circumstance, event, occupation, situation, tour

Strong + argument, commitment, criticism, demand, desire, evidence, feeling, growth, hand, influence, opinion, opposition, point, position, relationship, sense, support, supporter, lie, tradition, view

Substantial + amount, change, contribution, difference, evidence, improvement, increase, investment, loss, number, portion, profit, progress, proportion, sum, support

Sufficient + competence, condition, data, detail, evidence, fund, information, interest, money, protection, quantity, reason, resource, support, lime, understanding