When Jane began to take swimming lessons, her main ____ was the fear of water．

Many graduates in China do their best to go abroad to seek their______.

Achieving a high degree of proficiency in English as a foreign language is not a mysterious _____  without scientific basis.

Shelly had prepared carefully for her biology examination so that she could be sure of passing it on her first ______.

Some countries are increasing their use of natural gas, and other forms of ______.