The development of industry has been_______ gradual process throughout _______ human existence, from stone tools to modern technology.
If ____unsolved, the problem of food safety may lead to more serious results.
Jack is late again. It is ____of him to keep others waiting.
Though________money, his parents managed to send him to university.
It’s funny that Howard___ speak to you like your boss.
Helen has ____French and can speak fluently after a short stay with her aunt in Paris.