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The repeating unit ( c) may be a repeating unit which has a lactone structure as a polar group. 

The repeating unit which has a lactone structure is more preferably a repeating unit which is represented by General Formula (All) below. 

In General Formula (All), Rb$_{0 }$ represents a hydrogen atom, a halogen atom, or an alkyl group (preferably with 1 to 4 carbon atoms) which may have a substituent group. 

Examples of a preferable substituent group which the alkyl group of Rb$_{0 }$ may have include a hydroxyl group and a halogen atom. Examples of the halogen atom of Rb$_{0 }$ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. 

Rb$_{0 }$ is preferably a hydrogen atom, a methyl group, a hydroxy methyl group, and a trifluoromethyl group and particularly preferably a hydrogen atom and a methyl group. 

Ab represents a single bond, an alkylene group, a divalent linking group which has a monocyclic or polycyclic cycloalkyl structure, an ether bond, an ester bond, a carbonyl group, or a divalent linking group combining the above. Ab is preferably a single bond or a divalent linking group which is represented by -Ab$_{1 }$-CO$_{2}$-. 

Ab$_{1 }$ is a straight-chain or branched alkylene group and a monocyclic or polycyclic cycloalkylene group and prefer› ably a methylene group, an ethylene group, a cyclohexylene group, an adamantylene group, and a norbomylene group. 

V represents a group which has a lactone structure. 

As the group which has a lactone structure, it is possible to use any group as long as the group has a lactone structure; however, a ring lactone structure with 5 to 7 members is preferable and a lactone structure where another ring struc› ture is condensed in a form in which a bicyclo structure and a spiro structure are formed in a ring lactone structure with 5 to 7 members is preferable. It is more preferable to have a repeating unit which has a lactone structure which is represented by any of General Formulas (LCl-1) to (LCl- 17) below. In addition, the lactone structure may be directly bonded with the main chain. Preferable lactone structures are (LCl-1), (LCl-4), (LCl-5), (LCl-6), (LCl-8), (LCl- 13), and (LCl-14). 

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