Blockchain CBDE Exam Practice Test Instant Access

Question 1

A Mapping consists of keys and value.

Athe Keys can be anything, but the value can't be another mapping or struct.

Bthe Value can be anything, but the key cannot be another mapping, struct, integer or Boolean.

Cthe value can be anything, but the key cannot be another mapping, struct, enum or dynamically sized array.

Answer : C

Question 2

Block Difficulty:

Ais determined by the Ethereum Committee every fortnight to reflect the average amount of transaction and it cannot be influenced by the network itself.

Bincreases when the time between mined blocks is below 10 seconds, while it decreases when the time is above 20 seconds.

Cincreases when the time between mined blocks is below 20 seconds, while it decreases when the time is above 60 seconds.

Answer : B

Question 3

Transactions containing the same data to create the same smart contract are:

Aalways having the same signature.

Bhaving a different signature because of the nonce which changes upon every transaction.

Answer : B

Question 4

According to the official Style Guide:

Ayou should capitalize function names, events and contract names, to avoid confusion with JavaScript. You should use Tabs to indentation and a maximum of 80 characters per line.

Bcontract names should be capitalized, while functions should be mixedCase. You should use 4 spaces as indentation and a maximum of 79 (or 99) characters per line.

Ccontract should be mixedCase, as well as function names. Events should be capitalized. 2 spaces should be used as indentation and a maximum of 120 characters per line.

Answer : B

Question 5

GETH:

Ais the reference implementation of the Ethereum protocol and every other node implementation internally uses the closed-source from Geth.

Bis the library that is used for the blockchain node Go-Ethereum. It is also used by Parity is parts, because it's closed source.

Cis one of the many blockchain nodes that implement the Ethereum Protocol. It's open source and everyone can contribute.

Answer : C

Question 6

Having a bug-bounty program early on:

Acan help to engage the community in testing your smart contracts and therefore help to find bugs early.

Bmight be a burden as it is an administrative overhead mainly.

Cis completely useless. Who wants to test beta-ware software? It's better to start with the bug-bounty program after the contract is released on the main-net.

Answer : A

Question 7

The difference between address.send() and address.transfer() is:

A.send returns a Boolean and .transfer throws an exception on error. Both just forward the gasstipend of 2300 gas and are considered safe against re-entrancy.

B.send throws an exception and .transfer returns a Boolean on error. Both just forward the gasstipend of 2300 gas and considered safe against re-entrancy

C.send returns a Boolean and .transfer throws an exception on error. .send is considered dangerous, because it sends all gas along, while .transfer only sends the gas stipend of 2300 gas along

D.send and .transfer are both considered low-level functions which are dangerous, because they send all gas along. It's better to use address.call.value()() to control the gas-amount.

Answer : A

Blockchain CBDE BTA Certified Blockchain Developer - Ethereum Exam Practice Test