Estou tentando criar um programa para gerar aleatoriamente todas as perguntas de um tópico para minha revisão do GCSE. Meu código gera uma mensagem de erro após uma pergunta aleatória. Aqui está o meu código seguido pela mensagem de erro:

computing_UNIT4_networks = (["LOCAL AREA NETWORK","A network in one geographical area."],["WIDE AREA NETWORK","A network spanning two or more geographical areas."],["ROUTER","Connects a network to another network, sends and inspects packets of data."],["SWITCH","Channels data to its indented destination, within an internal network."],["NETWORK INTERFACE CARD","A card that allows a computer to connect to the network."],["FIBRE OPTIC CABLE","Uses light to transmit data."],["ETHERNET CABLE","Uses metal wires (usually copper) to transmit data."],["DNS","Used to match IP addresses to URL."],["HOSTING","Storing data for a user, usually a website."],["CLOUD COMPUTING","A remote computer is used to store data and provide services."])
computing_UNIT5_protocols = (["STAR NETWORK","All computers are connected 'individually' to the server.(using switches)"],["FULL MESH NETWORK","Every computer is connected to every other."],["ENCRYPTION","Disguising data so that it can be read with the key."],["DATA PACKET","Small unit of data to be transmitted."],["LATENCY","The delay in receiving data."],["BANDWIDTH","The amount of data that can be transmitted in a set amount of time."],["PACKET SWITCHING","Packets of data are transmitted and are able to take individual routes to their destination."],["CIRCUIT SWITCHING","Packets of data are transmitted along the same route to their destination."])
done = []
def computing():
    unit = int(input("Which UNIT are you revising?\n-"))
    if unit == 4:
        UNIT = computing_UNIT4_networks
        print("Here are",len(UNIT),"questions on UNIT4 - Wired and wireless networks.")
    elif unit == 5:
        UNIT = computing_UNIT5_protocols
        print("Here are",len(UNIT),"questions on UNIT5 - Network topologies, protocols and layers.")
    i=1
    c=0
    while i <= (len(UNIT)):
        import random
        randint=random.randint(0,len(UNIT))
        while randint in done:
            randint=random.randint(0,len(UNIT))
            if randint in done:
                i=i
            else: break
        question = UNIT[randint][1]
        answer = UNIT[randint][0]
        print("\nWhat is this the definition of?:",question)
        b=input("-").upper()
        if b == answer:
            c=c+1
            print("\nCorrect\nCurrent score:",c,"/",i)
        else: print("\nWrong. The answer was",answer,".\nCurrent score:",c,"/",i)
        done.append(randint)
        i = i+1
    print("\nYou scored",c,"/",len(UNIT),".")

computing()

Mensagem de erro:

Traceback (most recent call last):
  File "<pyshell#0>", line 1, in <module>
    computing()
  File "[FILELOCATION]", line 22, in computing
    question = UNIT[randint][1]
IndexError: tuple index out of range