New words：

certain ['sə:tn] adj. 肯定；确定；确信；无疑
make certain 弄确实；弄清楚；弄明白
for certain 肯定；确定；无疑

Sample Sentences：

We are certain to win the game.
I was certain that he had seen me.
There is no certain cure for this disease.
I can't say for certain when we'll arrive.
Please make certain when the train leaves.

New words：

malaria [məˈleriə] n. 疟疾

Sample Sentences：

Mosquitoes are carriers of malaria.
He fell sick with malaria on a trip to Africa.
There are many malaria sufferers in hospital.

New words：

ineffective [ini'fektiv] adj. 无效的；不起作用的；不奏效的
effectiveness [i'fektivnis] n. 效果；有效性；效能；效力；效率；成效
ineffectiveness [.inə'fektivnis] n. 无效；低效率；无能力

Sample Sentences：

An ineffective person should not be our leader.
The air-conditioner was ineffective in such a crowded room.
Scientists have carried out experiments to test the effectiveness of the new drug.

New words：

effect [ɪˈfekt] n. 影响；作用；效果；效应
effective [i'fektiv] adj. 有效的；生效的；实际的

Sample Sentences：

The drug has some bad side effects.
I can certainly feel the effects of too many late nights.

Window screens are effective in keeping out mosquitoes.
Their efforts to improve the production have been very effective.

New words：

input ['input] n. 投入；输入
output ['autput] n. 产量；输出

Sample Sentences：

Computers can now output data much more quickly.
I wanna increase our output to three kilos a week.

I have inputted the data into a computer.
Compared with the other crops, corn is a crop of less input but more output.