An action that is lavishly rewarded as soon as it is performed is well on its way to becoming a habit.

Since most doctors are ______ about effectiveness of th...

单项选择题Since most doctors are ______ about effectiveness of the new medicine, they seldom recommend it to their patients.

The manufacturers hoped that the motor show would _____...

单项选择题The manufacturers hoped that the motor show would ______ their car sales.