New words：

obstacle ['ɔbstəkl] n. 障碍；障碍物；阻碍；绊脚石

Sample Sentences：

To succeed, you must learn to overcome obstacles.
The biggest obstacle that we all face is our own internal fear.
Most competition cars will only roll over if they hit an obstacle.

internal [ɪnˈtɜːrnl] adj. 内心的；内部的；里面的；体内的；本身的

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