The 19th century reawakening in India, also known as the Indian Renaissance or Bengal Renaissance, refers to a period of intellectual, social, and cultural revival that took place in India during the 19th century. This movement was primarily driven by the upper middle classes in India. Therefore, the correct answer to the question is option 'A' - upper middle classes. Let's delve into the reasons behind this.

The Indian Renaissance emerged as a response to the social, political, and economic changes taking place in India under British colonial rule. It aimed to rejuvenate Indian society by promoting education, rational thinking, and social reform. The movement primarily focused on the urban areas where the educated middle class resided.

Historically, the upper middle classes in India were the most exposed to Western education and ideas due to their access to English education. They were the beneficiaries of the British education system and had the opportunity to study European philosophy, science, and literature. This exposure to Western knowledge influenced their thinking and made them more receptive to the ideas of social reform and cultural revival.

The upper middle classes played a crucial role in the Indian Renaissance as they were the ones who initiated and led various reform movements. They established organizations, such as the Brahmo Samaj and Arya Samaj, which aimed to reform social practices, promote education, and eradicate social evils. These organizations became the platforms for intellectual and cultural exchange, where like-minded individuals from the upper middle class could discuss and propagate their ideas.

Moreover, the upper middle classes had the financial resources and social capital required to support and sustain these reform movements. They had the means to establish schools, colleges, and libraries, which became centers of intellectual activities during the Indian Renaissance. The upper middle classes also had the social influence and connections to garner support from the ruling British government and spread their ideas among the wider population.

In contrast, the priestly classes and urban landlords did not have the same level of exposure to Western education and ideas. They were more entrenched in traditional customs and practices, which made them less receptive to the ideas of social reform and cultural revival. Additionally, the priestly classes were more focused on preserving their religious authority and maintaining the status quo, rather than engaging in intellectual and cultural pursuits.

In conclusion, the 19th century reawakening in India was primarily confined to the upper middle classes. Their exposure to Western education and ideas, financial resources, and social influence allowed them to initiate and lead the reform movements that characterized the Indian Renaissance. The priestly classes and urban landlords, on the other hand, were less involved in this movement due to their traditional mindset and lack of exposure to Western education.

During 19 century british rule on india so that era called upper middle class