What is one key characteristic of smart contracts in a blockchain network?

Smart contracts are designed to facilitate, verify, or enforce the negotiation and execution of contracts in an automated manner within blockchain networks. One key characteristic of smart contracts is that many of them can run concurrently. This concurrent execution allows multiple contracts to operate independently and simultaneously on the blockchain, leveraging the decentralized nature of the network to improve efficiency.

When smart contracts run concurrently, they can interact with one another and with the blockchain state, which enables complex applications and processes to be managed without blocking or waiting on single-threaded execution. This characteristic is essential for high-performance decentralized applications, as it efficiently utilizes the resources of the underlying blockchain infrastructure.

In contrast, the other options suggest limitations or constraints that don't accurately reflect the operational potential or intent behind smart contracts. For example, the notion that they only run sequentially is contrary to their intended design for efficiency. The idea that they must be deployed by trusted parties disregards the decentralized nature of most blockchain systems where trust is distributed. Finally, while reliability in code is desired, it is not an inherent guarantee of all smart contracts, as bugs and vulnerabilities can exist in the code.