Which of the following polymer is biodegradable?

1. (CH2-C|Cl=CH-CH2)n

2. (CH2-CH=CH-CH2-CH2-C|CNH)n

3. (O-CH-CH2-C-O-CH-CH2-C)n
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CH3OCH2CH3O

4. (N|N-(CN2)6-N|H-C||O-(CH2)4-C||O)n