26. [E] challenges
27. [J] searched
28. [D] categorizing
29. [K] similarities
30. [L] slightly
31. [G] percentage
32. [O] traditional
33. [I] regardless
34. [H] proving
35. [M] suggests
36. [I] It is possible for burglars to make jamming attacks with the necessary equipment and skill.
37. [D] Interfering with a wireless security system is similar to interfering with a conversation.
38. [J] A burglar has to continuously jam the wireless security device to avoid triggering the alarm, both inside and outside the house.
39. [F] SimpliSafe provides devices that are able to distinguish incidental radio interference from targeted jamming attacks.
40. [B] Only a very small proportion of burglaries are committed by technical means.
41. [H] It is difficult to crack SimpliSafe as its system keeps changing.
42. [C] Wireless devices will transmit signals so as to activate the alarm once something wrong is detected.
43. [K] Different measures should be taken to protect one's home from burglary in addition to the wireless security system.
44. [G] SimpliSafe's device can send a warning to the house owner's cellphone.
45. [E] Burglars can easily get a security device's frequency by Internet search.
46. [B] He intends to get rid of the tipping practice.
47. [B] It adds to the burden of ordinary customers.
48. [D] They can have some say in how much their servers earn.
49. [A] Service quality has little effect on tip size.
50. [D] Waiters should be paid by employers instead of customers.
51. [C] The impact of cheap oil on global economic growth.
52. [D] Consumers will spend their savings from cheap oil on other commodities.
53. [C] They use their money reserves to back up consumption.
54. [B] Its negative effects more than cancel out its positive effects
55. [A] People are not spending all the money they save on gas.