Chemistry revision 2017

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Question 1 of 1

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181920
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60
block

How many elements are there?

Select the correct answer(s).  

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181921
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120
none
181922
0
120
none
181923
0
120
none
181924
0
120
none
181925
0
180
none
181926
0
120
none
181927
0
120
none
181928
0
120
none
181929
0
120
none
181930
0
120
none
181931
0
120
none
181932
0
120
none
181933
0
120
none