Instead, it serves as the primary obstacle to the best opportunity for real educational reform: school choice.

"However, our primary obstacle is the station's own defensive screens."

Today, government regulation of cable television is the primary obstacle to competition.

Gravity is the primary obstacle to flight through the air.

Pretty soon, the primary obstacle for art lovers was figuring out visiting hours.

The cost of attending college is the primary obstacle facing undocumented students.

Many analysts said the primary obstacle to attracting more police candidates was pay.

Indeed, the primary obstacle to large-scale repatriation now is security.

The primary obstacle to bicycling is the motor vehicle in large numbers.

The primary obstacle, he said, is resistance from professional emergency crews.