CONTENTS 1
UNIT ONE 1
UNIT TWO 10
UNIT THREE 19
UNIT FOUR 28
UNIT FIVE 37
UNIT SIX： 44
UNIT SEVEN 52
UNIT EIGHT 61
UNIT NINE 71
UNIT TEN 80
UNIT ELEVEN 88
UNIT TWELVE 96
UNIT THIRTEEN 106
UNIT FOURTEEN 115
UNIT FIFTEEN 125
UNIT SIXTEEN 135
UNIT SEVENTEEN 145
VOCABULARY 156