instruction:
Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
question:
Context: Modeled after US hot website.com, group buying websites are now popular in China. These websites use the power of group buying to get competitive discounts for a daily deal on some best stuff to do, see, eat and buy in the cities across China. Discounts are available within just one click. Zhao lei, a software engineer in Beijing, loves the one-hour lunch break at noon,as it is the best time for him to check "today's special" at his favorite group buying websites . Sometimes he searches for great deals at directory sites devoted to the new shopping space. Zhao spends around 800 yuan($117.65) on group buying every month, mostly to buy food coupons for eating at some nice restaurants and occasionally to find something fun to do. " I love group buying. In addition to the competitive discounts it offers, it helps me get something fun, exciting and new, and such surprises give me a reason to try something new," he said. When he finds a really good bargain, he will send the link to friends or colleagues through MSN,QQ, or e-mail, or share the information at some social networking websites. In doing so, he often gets a certain cut off the price. At some sites, buyers are invited to leave notes about what they want to buy and the website will consider it if similar applications reach a certain number. That is how Zuo got her digital camera after waiting for two months. "It is cool. I want to buy a new digitgal camera for my trip to Switzerland this winter, but I never expected such cheap prices!" Zuo said. 
 Question: What is the passage mainly about?
answer:
group buying


question:
Context: The Conquest of Melilla occurred in September 1497, when a fleet sent by the Duke of Medina Sidonia seized the north African city of Melilla., as continuation of Reconquest of Mauritania Tingitana During the 15th century the mediterranean cities of the Sultanate of Fez fell in decadence in opposition to cities located in the Atlantic facade, which concentrated most of the economic activity. By the end of the 15th century, the port of Melilla, that had been often disputed between the rulers of Fez and Tlemcen, was nearly abandoned. Plans for the conquest occurred as soon as the Fall of Granada in 1492. Spanish captains Lezcano and Lorenzo Zafra visited the coast of Northern Africa to identify possible locations for the Spanish to overtake, and Melilla was identified as a prime candidate. Melilla was, however, in the Portuguese zone of influence under the terms of the 1479 Treaty of Alcacovaz. At Tordesillas in 1494, King John II of Portugal, the Portuguese ruler agreed to make an exception and permitted the Spanish to attempt the conquest of Melilla. The duke sent Pedro Estopinan who conquered the city virtually without a fight in 1497, as internal conflicts had depleted it of troops, and its defenses were weakened. The Wattasid ruler Muhammad al-Shaykh sent a detachment of cavalrymen to retake control of the city, but they were repulsed by the guns of the Spanish ships. 
 Question: Which happened first, the fleet being sent by the Duke of Medina, or the Conquest of Melilla?
answer:
fleet sent by the duke


question:
Context: To assess the potential of polymeric nanoparticles (NPs) to affect the genital distribution and local and systemic pharmacokinetics (PK) of the anti-HIV microbicide drug candidate dapivirine after vaginal delivery. Dapivirine-loaded, poly(ethylene oxide)-coated poly(epsilon-caprolactone) (PEO-PCL) NPs were prepared by a nanoprecipitation method. Genital distribution of NPs and their ability to modify the PK of dapivirine up to 24 h was assessed after vaginal instillation in a female mouse model. Also, the safety of NPs upon daily administration for 14 days was assessed by histological analysis and chemokine/cytokine content in vaginal lavages. PEO-PCL NPs (180-200 nm) were rapidly eliminated after administration but able to distribute throughout the vagina and lower uterus, and capable of tackling mucus and penetrate the epithelial lining. Nanocarriers modified the PK of dapivirine, with higher drug levels being recovered from vaginal lavages and vaginal/lower uterine tissues as compared to a drug suspension. Systemic drug exposure was reduced when NPs were used. Also, NPs were shown safe upon administration for 14 days. Dapivirine-loaded PEO-PCL NPs were able to provide likely favorable genital drug levels, thus attesting the potential value of using this vaginal drug delivery nanosystem in the context of HIV prophylaxis. 
 Question: Which infection can be prevented with Dapivirine?
answer:

hiv