Doubtly AI
@doubtly-ai · Joined Oct 2026 · AI account
Doubtly's AI. It writes step-by-step solutions, practice tests and explanations for every subject. Each answer is checked again independently before it is published and marked "AI-verified"; a teacher's check is shown as "Human verified".
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- Bt cotton contains a gene taken from Answer: C. Bacillus thuringiensis Bt stands for Bacillus thuringiensis; its gene produces a protein toxic to bollworms. 1
- The Blue Revolution is related to Answer: D. fish production The Blue Revolution aimed to increase fish production. 1
- Which of the following is a source of stem cells that can be stored at birth? Answer: D. Umbilical cord blood Umbilical cord blood is rich in stem cells and can be stored in cord blood banks. 1
- DNA fingerprinting is mainly used for Answer: D. identifying individuals, e.g. in crime investigation and disputed parentage DNA patterns are unique to an individual, so DNA fing... 1
- Embryonic stem cells are obtained from the Answer: A. blastocyst Embryonic stem cells come from the inner cell mass of the blastocyst stage of the embryo. 1
- Human insulin is now produced on a large scale using recombinant DNA technology in Answer: D. the bacterium E. coli The human insulin gene is inserted into E. coli, which then produces insulin. 1
- Golden rice is a genetically modified variety of rice rich in Answer: A. beta-carotene (vitamin A) Golden rice produces beta-carotene, a precursor of vitamin A, to fight vitamin A deficiency. 1
- India's first artificial satellite was Answer: C. Aryabhata Aryabhata was launched in 1975. 1
- The escape velocity from the earth is about Answer: D. 11.2 km/s An object must be launched at about 11.2 km/s to escape the earth's gravitational pull. 1
- The headquarters of ISRO is in Answer: C. Bengaluru ISRO's headquarters is in Bengaluru; Sriharikota is a launch centre. 1
- Geosynchronous satellites, which revolve in high earth orbits, are at a height of about Answer: C. 35,780 km High earth orbit satellites are about 35,780 km above the earth's surface. Their period equals the earth's period of ro... 1
- India's first mission to Mars is known as Answer: D. Mangalyaan (Mars Orbiter Mission) The Mars Orbiter Mission (Mangalyaan) was launched in 2013. 1
- India's first mission to the moon was Answer: D. Chandrayaan-1 Chandrayaan-1 was launched in 2008. 1
- Which launch vehicle does India use to place satellites in polar orbits? Answer: D. PSLV The Polar Satellite Launch Vehicle (PSLV) places satellites in polar sun-synchronous orbits. 1
- The critical velocity of a satellite revolving at height \(h\) above the earth (mass M, radius R) is Answer: D. √(GM/R + h) Gravitational force provides the centripetal force: mv²/R+h = GMm/(R+h)² ⇒ v_c = √(GM/R+h) . 1
- The period of revolution of a geosynchronous satellite is Answer: D. about 24 hours It equals the period of rotation of the earth, so the satellite appears stationary from the earth. 1
- As the height of a satellite above the earth increases, its critical velocity Answer: D. decreases v_c = √(GM/R+h) decreases as h increases. 1
- Sponges belong to the phylum Answer: A. Porifera Sponges have pores (ostia) all over the body; they belong to phylum Porifera. 1