Explanation:

HTTP is stateless, meaning it does not maintain session information between requests. Each request is independent  .

HTTP follows a request–response model, where the client initiates a request and the server responds. That means communication is always client → server → client, not simultaneous in both directions.

Although newer versions (like HTTP/1.1 with pipelining or HTTP/2 multiplexing) allow more efficient handling, HTTP is still fundamentally half-duplex—it’s not full duplex because only one side can actively send at a time.

Why not the other options?

(A) Stateful – Incorrect. HTTP doesn’t preserve state between requests  .

(C) Bidirectional – Incorrect. While data does go back and forth, it's not spontaneous from both ends; the server only responds after a request.

(D) Full duplex– Incorrect. Only one side transmits at a time; true full duplex (simultaneous two-way communication) is seen in protocols like WebSocket, not HTTP.

So, HTTP is best described as a stateless, unidirectional (half-duplex) request–response protocol.

Answer: (B) unidirectional

Explanation:

All the listed services — Twitter, Skype, and Gmail — are built on cloud-computing technology. Here's how:

• Twitter: Uses cloud infrastructure to scale, store tweets, and manage millions of concurrent users.
• Skype: Operates over the internet using cloud servers for voice/video calls and messaging.
• Gmail: A Google service entirely cloud-based, offering email access from anywhere via web and mobile apps.

These services rely on cloud computing for scalability, availability, storage, and performance.

Explanation:

Moderate anaerobes (also called microaerophiles) require low levels of oxygen, typically around 2–8%, for their growth.

• They cannot grow in atmospheric oxygen (~21%) but need some oxygen to survive.

Why other options are incorrect:

• (A) 0%: This corresponds to strict anaerobes that require no oxygen.
• (B) < 0.5%: Too low for moderate anaerobes.
• (D) 5 – 10%: Slightly higher, but generally microaerophiles prefer 2–8%.

Final Answer: (C) 2 – 8%

Explanation:

Aspartic acid (Asp) has a carboxyl group in its side chain that loses a proton at physiological pH (~7), making it negatively charged.

Why others are incorrect:

• (B) Histidine (His): Side chain is positively charged or neutral around pH 7 because its imidazole group has a pKa close to physiological pH but usually not negatively charged.
• (C) Tryptophan (Trp): Nonpolar, uncharged side chain.
• (D) Cysteine (Cys): Has a thiol group, which is mostly neutral at physiological pH (can be negatively charged but only under more alkaline conditions).

Final Answer: (A) Asp