Explanation:

The Arya Samaj was a Hindu reform movement founded by Swami Dayananda Saraswati in 1875. It aimed to promote the principles of monotheism, truth, and the Vedas while opposing idolatry, polytheism, and social evils prevalent in Hindu society at that time. The movement sought to bring about social and religious reform in order to restore the purity and simplicity of Vedic Hinduism.

The correct answer is option D: None of these. This means that all of the options mentioned in the question were criticized by the Arya Samaj. Let's examine each option in detail:

a) Idolatry and polytheism: The Arya Samaj strongly criticized idol worship and the belief in multiple gods. They believed in monotheism, emphasizing the worship of one Supreme Being, who they called "Brahma." They rejected the idea of a personal deity with physical form and advocated for the worship of the formless God.

b) Child marriage: The Arya Samaj vehemently opposed the practice of child marriage. They believed that child marriage violated the principles of morality and social justice. Swami Dayananda Saraswati actively campaigned against child marriage and advocated for the education and empowerment of women.

c) The taboo on foreign travel: The Arya Samaj criticized the prevailing taboo on foreign travel, which was prevalent in traditional Hindu society. They believed that travel and exposure to different cultures and ideas were essential for the intellectual and spiritual growth of individuals. Swami Dayananda Saraswati himself traveled extensively and encouraged others to do so as well.

In summary, the Arya Samaj criticized idolatry and polytheism, child marriage, and the taboo on foreign travel. They sought to reform Hindu society by promoting monotheism, opposing social evils, and advocating for education and women's empowerment. Therefore, the correct answer is option D: None of these.