【B】        Xenobots, named after the African clawed frog (Xenopus laevis), are synthetic lifeforms that aredesigned by computers to perform some desired functions and built by combining together differentbiological tissues. Whether xenobots are robots, organisms, or something else entirely remains asubject of debate among scientists.         The first xenobots were built by Douglas Blackiston according to blueprints generated byan AI program. Xenobots built to date have been less than one millimeter wide and composed of justtwo things: skin cells and heart muscle cells, both of which are derived from stem cells harvestedfrom early frog embryos. The skin cells provide rigid support and the heart cells act as small motors,contracting and expanding in volume to propel the xenobot forward. The shape of a xenobot’s bodyand its distribution of skin and heart cells are automatically designed in simulation to perform aspecific task, using a process of trial and error (an evolutionary algorithm).        Xenobots have beendesigned to walk, swim, push pellets, carry payloads, and work together in a swarm to aggregatedebris scattered along the surface of their dish into neat piles. They can survive for weeks withoutfood and heal themselves after lacerations.Xenobots can also self-replicate via “kinetic replication”—a process that is known to occur at themolecular level but has never been observed before at the scale of whole cells or organisms. They cangather loose stem cells in their environment and form them into new xenobots with the samecapability.       Currently, xenobots are primarily used as a scientific tool to understand how cells cooperate tobuild complex bodies during morphogenesis. However, the behavior and biocompatibility of currentxenobots suggest several potential applications to which they may be put in the future.        Given that xenobots are composed solely of frog cells, they are biodegradable. And as swarms ofxenobots tend to work together to push microscopic pellets in their dish into central piles, it has beenspeculated that future xenobots might be able do the same thing with microplastics in the ocean: findand aggregate tiny bits of plastic into a large ball of plastic that a traditional boat or drone can gatherand bring to a recycling center. Unlike traditional technologies, xenobots do not add additionalpollution as they work and degrade: they behave using energy from fat and protein naturally stored intheir tissue, which lasts about a week, at which point they simply turn into dead skin cells.In future clinical applications, such as targeted drug delivery, xenobots could be made from ahuman patient’s own cells, which would bypass the immune response challenges of other kindsof micro-robotic delivery systems. Such xenobots could potentially be used to scrape plaquefrom arteries, and with additional cell types and bioengineering, locate and treat diseases.
【題組】36. How do xenobots produce new xenobots?
(A)They collect loose stem cells and form them into new xenobots.
(B) They produce new xenobots by way of cell degradation.
(C) They use frog embryos to produce new xenobots.
(D)New xenobots could only be generated by computers.