Explanation

 the 1973 constitution of Pakistan was enacted on August 14, 1973

Zulifqar Ali Bhutto introduced a new constitution in Pakistan on August 14, 1973.

According to the 1973 constitution, both the national assembly and senate elect the president of Pakistan

whereas the prime minister is selected by the national assembly.

The Bicameral Legislature system was introduced for the first time in Pakistan in the constitution of 1973.

Khan Abdul Wali Khan was the opposition of the National Assembly at the time of promulgation.