All of the above are correct.
A revenue deficit occurs when the net income generated, (revenues minus expenditures), falls short of the projected net income. A revenue deficit impacts cash flow in future months. Revenue deficit should ideally be zero which would mean that government meets its day to day receipts. A high revenue deficit indicates a slippage in the fiscal consolidation path adopted by the government.

All of the above are correct.
In bicameral legislature, there is some difference between the powers of the two houses.
There are certain powers exercised only by Rajya Sabha like removing a matter from state list and adding to Union or Concurrent lists. There are certain powers exercised only by Lok Sabha like responsibility of Council of Ministers only to the Lok Sabha and not Rajya Sabha.
The powers of Lok Sabha are co-equal with Rajya Sabha in matters of introduction and passage of ordinary bills and non-money bills, Introduction and passage of constitutional amendment bills, election and impeachment of president and election and removal of the Vice-President.

Part IV contains Directive Principles of State Policy (DPSP) from Article 36 to Article 51. It guides the government in formulating policies to achieve the objective of welfare state.
Article 48A: The State shall endeavour to protect and improve the environment and to safeguard the forests and wildlife of the country.
Article 51A (f): It constitutes a part of Fundamental Duties – to value and preserve the rich heritage of our composite culture. Hence, (b) is the correct answer.
Article 45: The State shall endeavour to provide early childhood care and education to children below the age of six years.
Article 40: The State shall take steps to organize village panchayats and endow them with such powers and authority as may be necessary to enable them to function as units of self-government.

Statement 1 is incorrect while statement 2 is correct.

NASA and ISRO are collaborating on developing a satellite called NISAR, which will detect movements of the planet’s surface as small as 0.4 inches.
The name NISAR is short for NASA-ISRO-SAR. SAR here refers to the synthetic aperture radar that NASA will use to measure changes in the surface of the Earth. Essentially, SAR refers to a technique for producing high-resolution images. Because of the precision, the radar can penetrate clouds and darkness, which means that it can collect data day and night in any weather.
During the course of three years, the images will allow scientists to track changes in croplands, hazard sites and will help them to monitor crises such as volcanic eruptions. The images will be detailed enough to show local changes and broad enough to measure regional trends.

Statement 1 is correct while statement 2 is incorrect.
Asia-Pacific Economic Cooperation (APEC) is an inter-governmental forum for 21 Pacific Rim member economies that promotes free trade throughout the Asia-Pacific region.
Headquartered in Singapore, the APEC is recognized as one of the highest-level multilateral blocs and oldest forums in the Asia-Pacific region, and exerts a significant global influence.
India has requested membership in APEC, and received initial support from the United States, Japan, Australia and Papua New Guinea.
APEC’s 21 member economies are: Australia, Brunei Darussalam, Canada, Chile, Chinese Taipei, Hong Kong, Indonesia, Japan, Malaysia, Mexico, New Zealand, Papua New Guinea, People’s Republic of China, Peru, Republic of Korea, The Republic of the Philippines, The Russian Federation, Singapore, Thailand, United States of America and Vietnam.