inexpugnable

"Hooligans destroy unprovoked."

"The castle walls were impregnable, so the invaders gave up trying to enter. "

"The teacher's explanation of the math problem was logical and easy to follow. "

"My arguments for a later curfew were based on my good grades and responsible behavior. "

"It is hard work to swim against the current."

"It looks weaker and weaker, the more I think about it."

"Go easy on him: he is but a child."

"The teacher eliminated the confusing question from the test. "

"My grandmother used a soft felt hat for her winter walks. "

"The impossible of finishing the project by Friday became a reality when everyone worked late. "

"Despite her parents' disapproval, Sarah pursued her dream of becoming a musician. "

"My belief that hard work leads to success motivates me to study diligently. "