After Pakistan framed its first constitution in 1956, General Ayub Khan took over the administration of the country.

Below is a detailed explanation of how General Ayub Khan came to power and assumed control of the administration of Pakistan:

Background:
- Pakistan gained independence from British rule in 1947 and initially functioned as a dominion within the Commonwealth.
- Muhammad Ali Jinnah, also known as Quaid-e-Azam, served as Pakistan's first Governor-General until his death in 1948.
- After Jinnah's death, Liaquat Ali Khan became the Prime Minister of Pakistan.

Election of Constituent Assembly:
- In 1954, the Constituent Assembly of Pakistan was elected to draft the country's constitution.
- However, due to political instability and disagreements among various political parties, the process of constitution-making faced numerous challenges and delays.

Adoption of the First Constitution:
- Finally, on March 23, 1956, Pakistan adopted its first constitution, which declared the country an Islamic Republic.
- The constitution provided for a parliamentary form of government with a President as the Head of State and a Prime Minister as the Head of Government.

Assumption of Power by General Ayub Khan:
- Despite the adoption of the constitution, political instability and ineffectiveness of the civilian government continued to plague the country.
- In 1958, General Ayub Khan, who was serving as the Commander-in-Chief of the Pakistan Army, seized power in a military coup.
- Ayub Khan dissolved the Constituent Assembly, suspended the constitution, and imposed martial law in the country.
- He established a new governing body called the Supreme Council, with himself as the President.
- General Ayub Khan's administration introduced a new constitution in 1962, which established a presidential system of government.

Therefore, the correct answer is option 'D' - General Ayub Khan.