C．具有弱约束性 D．具有非约束性
26.{单选26}
27.{单选27}
28.{单选28}
29.{单选29}
30. {单选30}
31. {单选31}
32. {单选32}
33. {单选33}
34. {单选34}
35. {单选35}
36. {单选36}
37. {单选37}
38. {单选38}
39. {单选39}
40. {单选40}
41. {单选41}
42. {单选42}
43. {单选43}
44. {单选44}
45. {单选45}
46. {单选46}
47. {单选47}
48. {单选48}
49. {单选49}
50. {单选50}
