A terminal apparatus configured to communicate with a base station using a plurality of downlink component carriers, including a primary component carrier and a non-primary component carrier, and an uplink component carrier and to transmit a response signal indicating an error detection result of downlink data to the base station, where resources and constellation points to be used are determined through operation of Channel Selection, through an uplink control channel of the uplink component carrier based on an error detection result of a plurality of pieces of downlink data arranged in the plurality of downlink component carriers, the apparatus comprising: an extraction section configured to extract a downlink control channel signal from a received signal and extract downlink data from the received signal based on information on downlink data allocation resources; a decision section configured to make a blind decision as to whether or not control information is control information directed to the terminal apparatus, output information on the downlink data allocation resources for the terminal apparatus included in the control information directed to the terminal apparatus to the extraction section and identify a Control Channel Element, CCE, to which the control information directed to the terminal apparatus is mapped; a downlink data receiving section (210, 211) configured to receive the downlink data transmitted through at least one downlink data channel of the plurality of downlink component carriers; an error detection section configured to detect the presence or absence of a reception error of the received downlink data; and a control section configured to determine which PUCCH resource is used to transmit the response signal and which constellation point is set for the response signal based on success/failure in reception of a downlink allocation control signal in each downlink component carrier and error detection results from the error detection section; wherein when the error detection result regarding downlink data transmitted in the primary component carrier shows "no error" and when a downlink allocation control signal is not detected in the non-primary component carrier, the control section is configured to transmit the response signal using a first PUCCH resource determined in association with CCEs occupied by the downlink allocation control signal transmitted to the terminal apparatus in the primary component carrier, and wherein when a downlink allocation control signal is not detected in the primary component carrier and the error detection result regarding downlink data transmitted in the non-primary component carrier shows "no error", the control section is configured to transmit the response signal using a second PUCCH resource that is shared beforehand between base station and the terminal apparatus. an extraction section configured to extract a downlink control channel signal from a received signal and extract downlink data from the received signal based on information on downlink data allocation resources; a decision section configured to make a blind decision as to whether or not control information is control information directed to the terminal apparatus, output information on the downlink data allocation resources for the terminal apparatus included in the control information directed to the terminal apparatus to the extraction section and identify a Control Channel Element, CCE, to which the control information directed to the terminal apparatus is mapped; a downlink data receiving section (210, 211) configured to receive the downlink data transmitted through at least one downlink data channel of the plurality of downlink component carriers; an error detection section configured to detect the presence or absence of a reception error of the received downlink data; and a control section configured to determine which PUCCH resource is used to transmit the response signal and which constellation point is set for the response signal based on success/failure in reception of a downlink allocation control signal in each downlink component carrier and error detection results from the error detection section; wherein when the error detection result regarding downlink data transmitted in the primary component carrier shows "no error" and when a downlink allocation control signal is not detected in the non-primary component carrier, the control section is configured to transmit the response signal using a first PUCCH resource determined in association with CCEs occupied by the downlink allocation control signal transmitted to the terminal apparatus in the primary component carrier, and wherein when a downlink allocation control signal is not detected in the primary component carrier and the error detection result regarding downlink data transmitted in the non-primary component carrier shows "no error", the control section is configured to transmit the response signal using a second PUCCH resource that is shared beforehand between base station and the terminal apparatus.